WDIFF

draft-crispin-imapv-20.txt-225716.txt --> rfc3501.txt

Network Working Group M. Crispin
INTERNET-DRAFT: IMAP4rev1
Request for Comments: 3501 University of Washington
Obsoletes: 2060 October 2002
Document: internet-drafts/draft-crispin-imapv-20.txt March 2003
Category: Standards Track

INTERNET MESSAGE ACCESS PROTOCOL - VERSION 4rev1

Status of this Memo

This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC 2026.

This document is specifies an Internet-Draft. Internet-Drafts are working
documents of Internet standards track protocol for the
Internet Engineering Task Force (IETF), its areas, community, and its working groups. Note that other groups may also distribute
working documents as Internet-Drafts.

Internet-Drafts are draft documents valid for a maximum of six months requests discussion and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or suggestions for
improvements. Please refer to cite them other than as "work in progress."

To view the list Internet-Draft Shadow Directories, see
http://www.ietf.org/shadow.html.

A revised version current edition of this draft document will be submitted to the RFC
editor as an Proposed Standard "Internet
Official Protocol Standards" (STD 1) for the Internet Community.
Discussion and suggestions for improvement are requested, standardization state
and should
be sent to imap@CAC.Washington.EDU. This document will expire before
1 April 2003. status of this protocol. Distribution of this memo is unlimited.

This document is a revision of RFC 2060. Appendix B of this document
describes revisions and changes.

Abstract

The Internet Message Access Protocol, Version 4rev1 (IMAP4rev1)
allows a client to access and manipulate electronic mail messages on
a server. IMAP4rev1 permits manipulation of mailboxes (remote
message folders) in a way that is functionally equivalent to local
folders. IMAP4rev1 also provides the capability for an offline
client to resynchronize with the server (see also [IMAP-DISC]). server.

IMAP4rev1 includes operations for creating, deleting, and renaming
mailboxes;
mailboxes, checking for new messages; messages, permanently removing messages; messages,
setting and clearing flags; [RFC-2822] flags, RFC 2822 and [MIME-IMB] parsing;

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searching; RFC 2045 parsing, searching,
and selective fetching of message attributes, texts, and portions
thereof. Messages in IMAP4rev1 are accessed by the use of numbers.
These numbers are either message sequence numbers or unique
identifiers.

IMAP4rev1 supports a single server. A mechanism for accessing
configuration information to support multiple IMAP4rev1 servers is
discussed in [ACAP]. RFC 2244.

IMAP4rev1 does not specify a means of posting mail; this function is
handled by a mail transfer protocol such as [SMTP]. RFC 2821.

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RFC 3501 IMAPv4 March 2003

Table of Contents

IMAP4rev1 Protocol Specification ................................ 4
1. How to Read This Document ............................... 4
1.1. Organization of This Document

This document is written from the point of view of the implementor of
an IMAP4rev1 client or server. Beyond the protocol overview ........................... 4
1.2. Conventions Used in
section 2, it is not optimized for someone trying This Document ....................... 4
1.3. Special Notes to understand the
operation of the protocol. The material in sections 3 through Implementors ........................... 5
provides the general context and definitions with which IMAP4rev1
operates.

Sections 6, 7,
2. Protocol Overview ....................................... 6
2.1. Link Level .............................................. 6
2.2. Commands and 9 describe the IMAP commands, responses, Responses .................................. 6
2.2.1. Client Protocol Sender and
syntax, respectively. The relationships among these are such that it
is almost impossible to understand any of them separately. In
particular, do not attempt to deduce command syntax from the command
section alone; instead refer to the Formal Syntax section.

1.2. Conventions Used in This Document

"Conventions" are basic principles or procedures. Document
conventions are noted in this section.

In examples, "C:" Server Protocol Receiver ..... 6
2.2.2. Server Protocol Sender and "S:" indicate lines sent by the client Client Protocol Receiver ..... 7
2.3. Message Attributes ...................................... 8
2.3.1. Message Numbers ......................................... 8
2.3.1.1. Unique Identifier (UID) Message Attribute ....... 8
2.3.1.2. Message Sequence Number Message Attribute ....... 10
2.3.2. Flags Message Attribute ................................. 11
2.3.3. Internal Date Message Attribute ......................... 12
2.3.4. [RFC-2822] Size Message Attribute ....................... 12
2.3.5. Envelope Structure Message Attribute .................... 12
2.3.6. Body Structure Message Attribute ........................ 12
2.4. Message Texts ........................................... 13
3. State and
server respectively.

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "MAY", Flow Diagram .................................. 13
3.1. Not Authenticated State ................................. 13
3.2. Authenticated State ..................................... 13
3.3. Selected State .......................................... 13
3.4. Logout State ............................................ 14
4. Data Formats ............................................ 16
4.1. Atom .................................................... 16
4.2. Number .................................................. 16
4.3. String .................................................. 16
4.3.1. 8-bit and "OPTIONAL" in this document are to
be interpreted as described in [KEYWORDS].

The word "can" (not "may") is used to refer to a possible
circumstance or situation, as opposed to an optional facility of the
protocol.

"User" is used to refer to a human user, whereas "client" refers to
the software being run by the user.

"Connection" refers to the entire sequence of client/server
interaction from the initial establishment of the network connection
until its termination. "Session" refers to the sequence of
client/server interaction from the time that a mailbox is selected
(SELECT or EXAMINE command) until the time that selection ends
(SELECT or EXAMINE of another mailbox, CLOSE command, or connection
termination).

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Characters are 7-bit US-ASCII unless otherwise specified. Other
character sets are indicated using a "CHARSET", as described in
[MIME-IMT] and defined in [CHARSET]. CHARSETs have important
additional semantics in addition to defining character set; refer to
these documents for more detail.

There are several protocol conventions in IMAP. These refer to
aspects of the specification which are not strictly part of the IMAP
protocol, but which reflect generally-accepted practice.
Implementations need to be aware of these conventions, and avoid
conflicts whether or not they implement the convention. For example,
"&" may not be used as a hierarchy delimiter since it conflicts with
the Binary Strings ................................ 17
4.4. Parenthesized List ...................................... 17
4.5. NIL ..................................................... 17
5. Operational Considerations .............................. 18
5.1. Mailbox Naming .......................................... 18
5.1.1. Mailbox Hierarchy Naming ................................ 19
5.1.2. Mailbox Namespace Naming Convention ..................... 19
5.1.3. Mailbox International Naming Convention, Convention ................. 19
5.2. Mailbox Size and other uses of "&" Message Status Updates ................. 21
5.3. Response when no Command in
mailbox names are impacted as well.

1.3. Special Notes to Implementors

Implementors of the IMAP protocol are strongly encouraged to read the
IMAP implementation recommendations document [IMAP-IMPLEMENTATION] in
conjunction with this document, to help understand the intricacies of
this protocol and how best to build an interoperable product.

IMAP4rev1 is designed to be upwards compatible from the [IMAP2] and
unpublished IMAP2bis protocols. IMAP4rev1 is largely compatible with
the IMAP4 protocol described in RFC 1730; the exception being in
certain facilities added in RFC 1730 that proved problematic and were
subsequently removed. In the course of the evolution of IMAP4rev1,
some aspects in the earlier protocols have become obsolete. Obsolete
commands, responses, and data formats which an IMAP4rev1
implementation can encounter when used with an earlier implementation
are described in [IMAP-OBSOLETE].

Other compatibility issues with IMAP2bis, the most common variant of
the earlier protocol, are discussed in [IMAP-COMPAT]. A full
discussion of compatibility issues with rare (and presumed extinct)
variants of [IMAP2] is in [IMAP-HISTORICAL]; this document is
primarily of historical interest.

IMAP was originally developed for the older [RFC-822] standard, and
as a consequence several fetch items in IMAP incorporate "RFC822" Progress .................... 21
5.4. Autologout Timer ........................................ 22
5.5. Multiple Commands in
their name. With the exception of RFC822.SIZE, there are more modern
replacements; for example, the modern version of RFC822.HEADER is
BODY[HEADER.PEEK]. In all cases, "RFC822" should be interpreted as a
reference to the updated [RFC-2822] standard. Progress ........................... 22
6. Client Commands ........................................ 23
6.1. Client Commands - Any State ............................ 24
6.1.1. CAPABILITY Command ..................................... 24
6.1.2. NOOP Command ........................................... 25
6.1.3. LOGOUT Command ......................................... 26

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RFC 3501 IMAPv4 March 2003

2. Protocol Overview

2.1. Link Level

The IMAP4rev1 protocol assumes a reliable data stream such as
provided by TCP. When TCP is used, an IMAP4rev1 server listens on
port 143.

2.2.

6.2. Client Commands and Responses

An IMAP4rev1 connection consists of the establishment of a
client/server network connection, an initial greeting from the
server, and client/server interactions. These client/server
interactions consist of a client command, server data, and a server
completion result response.

All interactions transmitted by client and server are in the form of
lines; that is, strings that end with a CRLF. The protocol receiver
of an IMAP4rev1 client or server is either reading a line, or is
reading a sequence of octets with a known count followed by a line.

2.2.1. - Not Authenticated State .............. 26
6.2.1. STARTTLS Command ....................................... 27
6.2.2. AUTHENTICATE Command ................................... 28
6.2.3. LOGIN Command .......................................... 30
6.3. Client Protocol Sender and Commands - Authenticated State .................. 31
6.3.1. SELECT Command ......................................... 32
6.3.2. EXAMINE Command ........................................ 34
6.3.3. CREATE Command ......................................... 34
6.3.4. DELETE Command ......................................... 35
6.3.5. RENAME Command ......................................... 37
6.3.6. SUBSCRIBE Command ...................................... 39
6.3.7. UNSUBSCRIBE Command .................................... 39
6.3.8. LIST Command ........................................... 40
6.3.9. LSUB Command ........................................... 43
6.3.10. STATUS Command ......................................... 44
6.3.11. APPEND Command ......................................... 46
6.4. Client Commands - Selected State ....................... 47
6.4.1. CHECK Command .......................................... 47
6.4.2. CLOSE Command .......................................... 48
6.4.3. EXPUNGE Command ........................................ 49
6.4.4. SEARCH Command ......................................... 49
6.4.5. FETCH Command .......................................... 54
6.4.6. STORE Command .......................................... 58
6.4.7. COPY Command ........................................... 59
6.4.8. UID Command ............................................ 60
6.5. Client Commands - Experimental/Expansion ............... 62
6.5.1. X<atom> Command ........................................ 62
7. Server Protocol Receiver

The client command begins an operation. Each client command is
prefixed with an identifier (typically a short alphanumeric string,
e.g. A0001, A0002, etc.) called a "tag". A different tag Responses ....................................... 62
7.1. Server Responses - Status Responses .................... 63
7.1.1. OK Response ............................................ 65
7.1.2. NO Response ............................................ 66
7.1.3. BAD Response ........................................... 66
7.1.4. PREAUTH Response ....................................... 67
7.1.5. BYE Response ........................................... 67
7.2. Server Responses - Server and Mailbox Status ........... 68
7.2.1. CAPABILITY Response .................................... 68
7.2.2. LIST Response .......................................... 69
7.2.3. LSUB Response .......................................... 70
7.2.4 STATUS Response ........................................ 70
7.2.5. SEARCH Response ........................................ 71
7.2.6. FLAGS Response ......................................... 71
7.3. Server Responses - Mailbox Size ........................ 71
7.3.1. EXISTS Response ........................................ 71
7.3.2. RECENT Response ........................................ 72
7.4. Server Responses - Message Status ...................... 72
7.4.1. EXPUNGE Response ....................................... 72
7.4.2. FETCH Response ......................................... 73
7.5. Server Responses - Command Continuation Request ........ 79

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8. Sample IMAP4rev1 connection ............................ 80
9. Formal Syntax .......................................... 81
10. Author's Note .......................................... 92
11. Security Considerations ................................ 92
11.1. STARTTLS Security Considerations ....................... 92
11.2. Other Security Considerations .......................... 93
12. IANA Considerations .................................... 94
Appendices ..................................................... 95
A. References ............................................. 95
B. Changes from RFC 2060 .................................. 97
C. Key Word Index ......................................... 103
Author's Address ............................................... 107
Full Copyright Statement ....................................... 108

IMAP4rev1 Protocol Specification

1. How to Read This Document

1.1. Organization of This Document

This document is
generated by written from the point of view of the implementor of
an IMAP4rev1 client for each command.

Clients MUST follow or server. Beyond the syntax outlined protocol overview in this specification
strictly. It
section 2, it is a syntax error to send a command with missing or
extraneous spaces or arguments.

There are two cases in which a line from the client does not
represent a complete command. In one case, a command argument is
quoted with an octet count (see the description of literal in String
under Data Formats); in the other case, the command arguments require
server feedback (see the AUTHENTICATE command). In either case, the
server sends a command continuation request response if it is ready optimized for someone trying to understand the octets (if appropriate) and the remainder
operation of the command.
This response is prefixed with the token "+".

Note: If, instead, the server detected an error protocol. The material in sections 3 through 5
provides the
command, it sends a BAD completion response general context and definitions with tag
matching the command (as described below) to reject the
command which IMAP4rev1
operates.

Sections 6, 7, and prevent 9 describe the client from sending IMAP commands, responses, and
syntax, respectively. The relationships among these are such that it
is almost impossible to understand any more of the
command.

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It is also possible for the server them separately. In
particular, do not attempt to send a completion
response for some other deduce command (if multiple commands are syntax from the command
section alone; instead refer to the Formal Syntax section.

1.2. Conventions Used in progress), This Document

"Conventions" are basic principles or untagged data. procedures. Document
conventions are noted in this section.

In either case, the
command continuation request is still pending; examples, "C:" and "S:" indicate lines sent by the client
takes the appropriate action for the response, and reads
another response from the server. In all cases, the client
MUST send a complete command (including receiving all
command continuation request responses
server respectively.

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "MAY", and command
continuations for the command) before initiating a new
command. "OPTIONAL" in this document are to
be interpreted as described in [KEYWORDS].

The protocol receiver of an IMAP4rev1 server reads word "can" (not "may") is used to refer to a command line
from the client, parses possible
circumstance or situation, as opposed to an optional facility of the command and its arguments, and transmits
server data and
protocol.

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RFC 3501 IMAPv4 March 2003

"User" is used to refer to a server command completion result response.

2.2.2. Server Protocol Sender and Client Protocol Receiver

Data transmitted human user, whereas "client" refers to
the software being run by the server user.

"Connection" refers to the client and status responses
that do not indicate command completion are prefixed with entire sequence of client/server
interaction from the token
"*", and are called untagged responses.

Server data MAY be sent as a result initial establishment of a client command, or MAY be
sent unilaterally by the server. There is no syntactic difference
between server data that resulted from a specific command and server
data that were sent unilaterally.

The server completion result response indicates network connection
until its termination.

"Session" refers to the success or
failure sequence of client/server interaction from
the operation. It time that a mailbox is tagged with the same tag as selected (SELECT or EXAMINE command) until
the
client command which began the operation. Thus, if more than one
command is time that selection ends (SELECT or EXAMINE of another mailbox,
CLOSE command, or connection termination).

Characters are 7-bit US-ASCII unless otherwise specified. Other
character sets are indicated using a "CHARSET", as described in progress, the tag
[MIME-IMT] and defined in a server completion response
identifies the command [CHARSET]. CHARSETs have important
additional semantics in addition to which the response applies. defining character set; refer to
these documents for more detail.

There are
three possible server completion responses: OK (indicating success),
NO (indicating failure), or BAD (indicating several protocol error such as
unrecognized command or command syntax error).

Servers SHOULD enforce the syntax outlined conventions in this IMAP. These refer to
aspects of the specification
strictly. Any client command with a protocol syntax error, including
(but which are not limited to) missing or extraneous spaces or arguments,
SHOULD strictly part of the IMAP
protocol, but reflect generally-accepted practice. Implementations
need to be rejected, aware of these conventions, and avoid conflicts whether or
not they implement the client given convention. For example, "&" may not be used
as a BAD server completion
response.

The hierarchy delimiter since it conflicts with the Mailbox
International Naming Convention, and other uses of "&" in mailbox
names are impacted as well.

1.3. Special Notes to Implementors

Implementors of the IMAP protocol receiver are strongly encouraged to read the
IMAP implementation recommendations document [IMAP-IMPLEMENTATION] in
conjunction with this document, to help understand the intricacies of
this protocol and how best to build an interoperable product.

IMAP4rev1 client reads a response line is designed to be upwards compatible from the server. It then takes action on the response based upon the
first token of the response, which can be a tag, a "*", or a "+".

A client MUST be prepared to accept any server response at all times.
This includes server data that was not requested. Server data SHOULD

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be recorded, so that the client can reference its recorded copy
rather than sending a command to is largely compatible with
the server to request IMAP4 protocol described in RFC 1730; the data. exception being in
certain facilities added in RFC 1730 that proved problematic and were
subsequently removed. In the case course of certain server data, the data MUST be recorded.

This topic is discussed in greater detail in the Server Responses
section.

2.3. Message Attributes

In addition to message text, each message has several attributes
associated with it. These attributes can be retrieved individually
or in conjunction with other attributes or message texts.

2.3.1. Message Numbers

Messages in IMAP4rev1 are accessed by one evolution of two numbers; IMAP4rev1,
some aspects in the unique
identifier earlier protocols have become obsolete. Obsolete
commands, responses, and the message sequence number.

2.3.1.1. Unique Identifier (UID) Message Attribute

A 32-bit value assigned to each message, data formats which an IMAP4rev1
implementation can encounter when used with the
unique identifier validity value (see below) forms a 64-bit value
that MUST NOT refer to any other message an earlier implementation
are described in the mailbox or any
subsequent mailbox [IMAP-OBSOLETE].

Other compatibility issues with IMAP2bis, the same name forever. Unique identifiers most common variant of
the earlier protocol, are assigned discussed in a strictly ascending fashion [IMAP-COMPAT]. A full
discussion of compatibility issues with rare (and presumed extinct)

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RFC 3501 IMAPv4 March 2003

variants of [IMAP2] is in [IMAP-HISTORICAL]; this document is
primarily of historical interest.

IMAP was originally developed for the mailbox; older [RFC-822] standard, and
as each
message is added to a consequence several fetch items in IMAP incorporate "RFC822" in
their name. With the mailbox it exception of RFC822.SIZE, there are more modern
replacements; for example, the modern version of RFC822.HEADER is assigned
BODY.PEEK[HEADER]. In all cases, "RFC822" should be interpreted as a higher UID than
reference to the
message(s) which were added previously. Unlike message sequence
numbers, unique identifiers are not necessarily contiguous. updated [RFC-2822] standard.

2. Protocol Overview

2.1. Link Level

The unique identifier IMAP4rev1 protocol assumes a reliable data stream such as that
provided by TCP. When TCP is used, an IMAP4rev1 server listens on
port 143.

2.2. Commands and Responses

An IMAP4rev1 connection consists of the establishment of a message MUST NOT change during
client/server network connection, an initial greeting from the
session,
server, and SHOULD NOT change between sessions. Any change client/server interactions. These client/server
interactions consist of
unique identifiers between sessions MUST be detectable using the
UIDVALIDITY mechanism discussed below. Persistent unique identifiers
are required for a client to resynchronize its state from command, server data, and a previous
session with the server (e.g. disconnected or offline access
clients); this is discussed further in [IMAP-DISC].

Associated with every mailbox
completion result response.

All interactions transmitted by client and server are two values which aid in unique
identifier handling: the next unique identifier value and the unique
identifier validity value. form of
lines, that is, strings that end with a CRLF. The next unique protocol receiver
of an IMAP4rev1 client or server is either reading a line, or is
reading a sequence of octets with a known count followed by a line.

2.2.1. Client Protocol Sender and Server Protocol Receiver

The client command begins an operation. Each client command is
prefixed with an identifier value (typically a short alphanumeric string,
e.g., A0001, A0002, etc.) called a "tag". A different tag is
generated by the predicted value that will be
assigned client for each command.

Clients MUST follow the syntax outlined in this specification
strictly. It is a syntax error to send a new message command with missing or
extraneous spaces or arguments.

There are two cases in which a line from the mailbox. Unless client does not
represent a complete command. In one case, a command argument is
quoted with an octet count (see the unique
identifier validity also changes description of literal in String
under Data Formats); in the other case, the command arguments require
server feedback (see below), the next unique
identifier value MUST have AUTHENTICATE command). In either case, the following two characteristics. First,

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RFC 3501 IMAPv4 March 2003

server sends a command continuation request response if it is ready
for the next unique identifier value MUST NOT change unless new messages
are added to the mailbox; octets (if appropriate) and second, the next unique identifier
value MUST change whenever new messages are added to remainder of the mailbox,
even if those new messages are subsequently expunged.

Note: The next unique identifier value command.
This response is intended to
provide prefixed with the token "+".

Note: If instead, the server detected an error in the
command, it sends a means for BAD completion response with a client to determine whether any
messages have been delivered tag
matching the command (as described below) to reject the mailbox since
command and prevent the
previous time it checked this value. It is not intended to
provide any guarantee that any message will have this
unique identifier. A client can only assume, at the time
that it obtains from sending any more of the next unique identifier value, that
messages which arrive after that time will have a UID that
command.

It is greater than or equal also possible for the server to that value.

The unique identifier validity value is sent in an UIDVALIDITY send a completion
response code for some other command (if multiple commands are
in an OK progress), or untagged response at mailbox selection time.
If unique identifiers from an earlier session fail to persist to this
session, data. In either case, the unique identifier validity value MUST be greater than
command continuation request is still pending; the one used in client
takes the earlier session.

Note: Ideally, unique identifiers SHOULD persist at all
times. Although this specification recognizes that failure
to persist can be unavoidable in certain server
environments, it STRONGLY ENCOURAGES message store
implementation techniques that avoid this problem. For
example:

1) Unique identifiers MUST be strictly ascending in appropriate action for the
mailbox at response, and reads
another response from the server. In all times. If cases, the physical message store is
re-ordered by client
MUST send a non-IMAP agent, this requires that the
unique identifiers in the mailbox be regenerated, since complete command (including receiving all
command continuation request responses and command
continuations for the
former unique identifiers are no longer strictly ascending
as command) before initiating a result new
command.

The protocol receiver of an IMAP4rev1 server reads a command line
from the re-ordering.

2) If client, parses the message store has no mechanism to store unique
identifiers, it must regenerate unique identifiers at each
session, command and each session must have a unique UIDVALIDITY
value.

3) If the mailbox is deleted its arguments, and transmits
server data and a new mailbox with the
same name is created at a later date, server command completion result response.

2.2.2. Server Protocol Sender and Client Protocol Receiver

Data transmitted by the server must
either keep track of unique identifiers from to the previous
instance of client and status responses
that do not indicate command completion are prefixed with the mailbox, or it must assign token
"*", and are called untagged responses.

Server data MAY be sent as a new
UIDVALIDITY value to the new instance result of a client command, or MAY be
sent unilaterally by the mailbox. A
good UIDVALIDITY value to use in this case server. There is no syntactic difference
between server data that resulted from a 32-bit
representation of specific command and server
data that were sent unilaterally.

The server completion result response indicates the creation date/time success or
failure of the mailbox. operation. It is alright to use a constant such tagged with the same tag as 1, but only the
client command which began the operation. Thus, if it

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guaranteed that unique identifiers will never be reused,
even more than one
command is in progress, the case of tag in a mailbox being deleted (or renamed)
and server completion response
identifies the command to which the response applies. There are
three possible server completion responses: OK (indicating success),
NO (indicating failure), or BAD (indicating a new mailbox by protocol error such as
unrecognized command or command syntax error).

Servers SHOULD enforce the same name created at some future
time.

4) syntax outlined in this specification
strictly. Any client command with a protocol syntax error, including
(but not limited to) missing or extraneous spaces or arguments,

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RFC 3501 IMAPv4 March 2003

SHOULD be rejected, and the client given a BAD server completion
response.

The combination protocol receiver of mailbox name, UIDVALIDITY, and UID
must refer to an IMAP4rev1 client reads a single immutable message response line
from the server. It then takes action on that server
forever. In particular, the internal date, [RFC-2822]
size, envelope, body structure, and message texts (RFC822,
RFC822.HEADER, RFC822.TEXT, and response based upon the
first token of the response, which can be a tag, a "*", or a "+".

A client MUST be prepared to accept any server response at all BODY[...] fetch data
items) must never change. times.
This does includes server data that was not include message
numbers, nor does it include attributes requested. Server data SHOULD
be recorded, so that the client can be set by reference its recorded copy
rather than sending a STORE command (e.g. FLAGS).

2.3.1.2. Message Sequence Number Message Attribute

A relative position from 1 to the number of messages in server to request the mailbox.
This position data. In
the case of certain server data, the data MUST be ordered by ascending unique identifier. As
each new message is added, it is assigned a message sequence number
that recorded.

This topic is 1 higher than the number of messages discussed in greater detail in the mailbox before
that new message was added. Server Responses
section.

2.3. Message sequence numbers Attributes

In addition to message text, each message has several attributes
associated with it. These attributes can be reassigned during retrieved individually
or in conjunction with other attributes or message texts.

2.3.1. Message Numbers

Messages in IMAP4rev1 are accessed by one of two numbers; the session. For
example, unique
identifier or the message sequence number.

2.3.1.1. Unique Identifier (UID) Message Attribute

A 32-bit value assigned to each message, which when used with the
unique identifier validity value (see below) forms a 64-bit value
that MUST NOT refer to any other message is permanently removed (expunged) from in the
mailbox, mailbox or any
subsequent mailbox with the same name forever. Unique identifiers
are assigned in a strictly ascending fashion in the mailbox; as each
message sequence number for all subsequent messages is
decremented. The number of messages in added to the mailbox it is also
decremented. Similarly, a new message can be assigned a higher UID than the
message(s) which were added previously. Unlike message sequence number that was once held by some other
numbers, unique identifiers are not necessarily contiguous.

The unique identifier of a message prior to an
expunge.

In addition to accessing messages by relative position in MUST NOT change during the
mailbox, message sequence numbers can be used in mathematical
calculations. For example, if an untagged "11 EXISTS" is received,
session, and previously an untagged "8 EXISTS" was received, three new
messages have arrived with message sequence numbers SHOULD NOT change between sessions. Any change of 9, 10, and 11.
Another example; if message 287 in a 523 message mailbox has UID
12345, there
unique identifiers between sessions MUST be detectable using the
UIDVALIDITY mechanism discussed below. Persistent unique identifiers
are exactly 286 messages which have lesser UIDs and 236
messages which have greater UIDs.

2.3.2. Flags Message Attribute

A list of zero or more named tokens associated required for a client to resynchronize its state from a previous
session with the message. A
flag is set by its addition to server (e.g., disconnected or offline access
clients); this list, and is cleared by its
removal. There are two types of flags discussed further in IMAP4rev1. A flag of
either type can be permanent or session-only. [IMAP-DISC].

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RFC 3501 IMAPv4 March 2003

A system flag is a flag name that is pre-defined in this
specification. All system flags begin

Associated with "\". Certain system
flags (\Deleted every mailbox are two values which aid in unique
identifier handling: the next unique identifier value and \Seen) have special semantics described
elsewhere. the unique
identifier validity value.

The currently-defined system flags are:

\Seen
Message has been read

\Answered
Message has been answered

\Flagged
Message is "flagged" for urgent/special attention

\Deleted
Message is "deleted" for removal by later EXPUNGE

\Draft
Message has not completed composition (marked as a draft).

\Recent
Message is "recently" arrived in this mailbox. This session next unique identifier value is the first session predicted value that will be
assigned to a new message in the mailbox. Unless the unique
identifier validity also changes (see below), the next unique
identifier value MUST have been notified about this
message; if the session is read-write, subsequent sessions
will not see \Recent set for this message. This flag can not
be altered by following two characteristics. First,
the client.

If it next unique identifier value MUST NOT change unless new messages
are added to the mailbox; and second, the next unique identifier
value MUST change whenever new messages are added to the mailbox,
even if those new messages are subsequently expunged.

Note: The next unique identifier value is not possible intended to
provide a means for a client to determine whether or not any
messages have been delivered to the mailbox since the
previous time it checked this
session value. It is the first session not intended to be notified about a message,
then
provide any guarantee that any message SHOULD be considered recent.

If multiple connections will have this
unique identifier. A client can only assume, at the same mailbox selected
simultaneously, time
that it is undefined which of these connections
will see newly-arrived obtains the next unique identifier value, that
messages with \Recent set and which arriving after that time will see it without \Recent set.

A keyword is defined by the server implementation. Keywords do not
begin with "\". Servers MAY permit the client have a UID greater
than or equal to define new keywords that value.

The unique identifier validity value is sent in the mailbox (see the description of the PERMANENTFLAGS a UIDVALIDITY
response code for more information).

A flag can be permanent or session-only on a per-flag basis.
Permanent flags are those which the client can add or remove from the
message flags permanently; that is, concurrent and subsequent
sessions will see any change in permanent flags. Changes to an OK untagged response at mailbox selection time.
If unique identifiers from an earlier session
flags are valid only fail to persist in that this
session, the unique identifier validity value MUST be greater than
the one used in the earlier session.

Note: The \Recent system flag is a special case of a

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session flag. \Recent Ideally, unique identifiers SHOULD persist at all
times. Although this specification recognizes that failure
to persist can not be used as an argument unavoidable in a
STORE or APPEND command, and thus can not certain server
environments, it STRONGLY ENCOURAGES message store
implementation techniques that avoid this problem. For
example:

1) Unique identifiers MUST be changed strictly ascending in the
mailbox at
all.

2.3.3. Internal Date Message Attribute

The internal date and time of all times. If the physical message on the server. This store is not
the date and time in the [RFC-2822] header, but rather
re-ordered by a date and
time which reflects when non-IMAP agent, this requires that the message was received. In
unique identifiers in the case of
messages delivered via [SMTP], this SHOULD mailbox be regenerated, since
the date and time of
final delivery of the message former unique identifiers are no longer strictly
ascending as defined by [SMTP]. In the case a result of
messages delivered by the IMAP4rev1 COPY command, this SHOULD be re-ordering.

2) If the
internal date message store has no mechanism to store unique
identifiers, it must regenerate unique identifiers at
each session, and time of the source message. In the case of
messages delivered by the IMAP4rev1 APPEND command, this SHOULD be each session must have a unique
UIDVALIDITY value.

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RFC 3501 IMAPv4 March 2003

3) If the date mailbox is deleted and time as specified in a new mailbox with the APPEND command description.
All other cases are implementation defined.

2.3.4. [RFC-2822] Size Message Attribute

The number of octets in
same name is created at a later date, the message, as expressed in [RFC-2822]
format.

2.3.5. Envelope Structure Message Attribute

A parsed representation server must
either keep track of unique identifiers from the [RFC-2822] header
previous instance of the message.
Note that mailbox, or it must assign a
new UIDVALIDITY value to the IMAP Envelope structure is not new instance of the same as an [SMTP]
envelope.

2.3.6. Body Structure Message Attribute
mailbox. A parsed good UIDVALIDITY value to use in this case
is a 32-bit representation of the [MIME-IMB] body structure information creation date/time of
the message.

2.4. Message Texts

In addition to being able mailbox. It is alright to fetch use a constant such as
1, but only if it guaranteed that unique identifiers
will never be reused, even in the full [RFC-2822] text case of a
message, IMAP4rev1 permits mailbox
being deleted (or renamed) and a new mailbox by the fetching of portions
same name created at some future time.

4) The combination of the full
message text. Specifically, it is possible mailbox name, UIDVALIDITY, and UID
must refer to fetch the [RFC-2822]
message header, [RFC-2822] message body, a [MIME-IMB] single immutable message on that server
forever. In particular, the internal date, [RFC-2822]
size, envelope, body part, or a
[MIME-IMB] header.

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3. State structure, and Flow Diagram

Once the connection between client message texts
(RFC822, RFC822.HEADER, RFC822.TEXT, and server is established, an
IMAP4rev1 connection is in one of four states. The initial state is
identified in the server greeting. Most commands are only valid in
certain states. It is a protocol error for the client to attempt all BODY[...]
fetch data items) must never change. This does not
include message numbers, nor does it include attributes
that can be set by a STORE command while (e.g., FLAGS).

2.3.1.2. Message Sequence Number Message Attribute

A relative position from 1 to the connection is number of messages in an inappropriate state, and the
server will respond with a BAD or NO (depending upon server
implementation) command completion result.

3.1. Not Authenticated State

In not authenticated state, the client mailbox.
This position MUST supply authentication
credentials before most commands will be permitted. This state ordered by ascending unique identifier. As
each new message is
entered when added, it is assigned a connection starts unless message sequence number
that is 1 higher than the connection has been
pre-authenticated.

3.2. Authenticated State

In authenticated state, number of messages in the client is authenticated and MUST select a mailbox to access before commands
that affect messages will new message was added.

Message sequence numbers can be
permitted. This state is entered when a pre-authenticated connection
starts, reassigned during the session. For
example, when acceptable authentication credentials have been
provided, after an error in selecting a message is permanently removed (expunged) from the
mailbox, or after a
successful CLOSE command.

3.3. Selected State

In selected state, a mailbox has been selected to access. This state the message sequence number for all subsequent messages is entered when a mailbox has been successfully selected.

3.4. Logout State

In logout state,
decremented. The number of messages in the connection mailbox is being terminated. This state also
decremented. Similarly, a new message can be entered as a result of assigned a client request (via the LOGOUT command)
or message
sequence number that was once held by unilateral action on the part of either the client or server.

If the client requests logout state, some other message prior to an
expunge.

In addition to accessing messages by relative position in the server MUST send
mailbox, message sequence numbers can be used in mathematical
calculations. For example, if an untagged
BYE response "11 EXISTS" is received,
and previously an untagged "8 EXISTS" was received, three new
messages have arrived with message sequence numbers of 9, 10, and 11.
Another example, if message 287 in a tagged OK response to the LOGOUT command before
the server closes the connection; 523 message mailbox has UID
12345, there are exactly 286 messages which have lesser UIDs and the client MUST read the tagged
OK response to the LOGOUT command before the client closes the
connection.

A server MUST NOT unilaterally close the connection without sending 236
messages which have greater UIDs.

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RFC 3501 IMAPv4 March 2003

an untagged BYE response that contains the reason for having done so.

2.3.2. Flags Message Attribute

A client SHOULD NOT unilaterally close list of zero or more named tokens associated with the connection, message. A
flag is set by its addition to this list, and instead
SHOULD issue is cleared by its
removal. There are two types of flags in IMAP4rev1. A flag of
either type can be permanent or session-only.

A system flag is a LOGOUT command. flag name that is pre-defined in this
specification. All system flags begin with "\". Certain system
flags (\Deleted and \Seen) have special semantics described
elsewhere. The currently-defined system flags are:

\Seen
Message has been read

\Answered
Message has been answered

\Flagged
Message is "flagged" for urgent/special attention

\Deleted
Message is "deleted" for removal by later EXPUNGE

\Draft
Message has not completed composition (marked as a draft).

\Recent
Message is "recently" arrived in this mailbox. This session
is the first session to have been notified about this
message; if the session is read-write, subsequent sessions
will not see \Recent set for this message. This flag can not
be altered by the client.

If it is not possible to determine whether or not this
session is the server detects first session to be notified about a message,
then that message SHOULD be considered recent.

If multiple connections have the client
has unilaterally closed the connection, same mailbox selected
simultaneously, it is undefined which of these connections
will see newly-arrived messages with \Recent set and which
will see it without \Recent set.

A keyword is defined by the server implementation. Keywords do not
begin with "\". Servers MAY omit permit the
untagged BYE response and simply close its connection.

+----------------------+
|connection established|
+----------------------+
||
\/
+--------------------------------------+
| server greeting |
+--------------------------------------+
|| (1) || (2) || (3)
\/ || ||
+-----------------+ || ||
|Not Authenticated| || ||
+-----------------+ || ||
|| (7) || (4) || ||
|| \/ \/ ||
|| +----------------+ ||
|| | Authenticated |<=++ ||
|| +----------------+ || ||
|| || (7) || (5) || (6) ||
|| || \/ || ||
|| || +--------+ || ||
|| || |Selected|==++ ||
|| || +--------+ ||
|| || || (7) ||
\/ \/ \/ \/
+--------------------------------------+
| Logout |
+--------------------------------------+
||
\/
+-------------------------------+
|both sides close client to define new keywords
in the connection|
+-------------------------------+

(1) connection without pre-authentication (OK greeting)
(2) pre-authenticated connection (PREAUTH greeting)
(3) rejected connection (BYE greeting)
(4) successful LOGIN or AUTHENTICATE command
(5) successful SELECT or EXAMINE command
(6) CLOSE command, or failed SELECT or EXAMINE command
(7) LOGOUT command, server shutdown, or connection closed mailbox (see the description of the PERMANENTFLAGS response
code for more information).

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4. Data Formats

IMAP4rev1 uses textual commands and responses. Data in IMAP4rev1

A flag can be in one of several forms: atom, number, string, parenthesized list, permanent or NIL. Note session-only on a per-flag basis.
Permanent flags are those which the client can add or remove from the
message flags permanently; that is, concurrent and subsequent
sessions will see any change in permanent flags. Changes to session
flags are valid only in that session.

Note: The \Recent system flag is a particular data item may take more than one
form; for example, special case of a data item defined as using "astring" syntax may
session flag. \Recent can not be either used as an atom or argument in a string.

4.1. Atom

An atom consists of one or more non-special characters.

4.2. Number

A number consists of one
STORE or more digit characters, APPEND command, and represents a
numeric value.

4.3. String

A string is in one of two forms: either literal or quoted string. thus can not be changed at
all.

2.3.3. Internal Date Message Attribute

The literal form is the general form internal date and time of string. The quoted string
form is an alternative that avoids the overhead of processing a
literal at message on the cost of limitations of characters which may be used.

A literal server. This
is a sequence of zero or more octets (including CR not the date and LF),
prefix-quoted with an octet count time in the form of an open brace ("{"),
the number of octets, close brace ("}"), [RFC-2822] header, but rather a
date and CRLF. time which reflects when the message was received. In
the case of
literals transmitted from server to client, messages delivered via [SMTP], this SHOULD be the CRLF is immediately
followed by
date and time of final delivery of the octet data. message as defined by
[SMTP]. In the case of literals transmitted from
client to server, messages delivered by the client MUST wait to receive a command
continuation request (described later in IMAP4rev1 COPY
command, this document) before
sending the octet data (and SHOULD be the remainder internal date and time of the command).

A quoted string is a sequence source
message. In the case of zero or more 7-bit characters,
excluding CR and LF, with double quote (<">) characters at each end. messages delivered by the IMAP4rev1
APPEND command, this SHOULD be the date and time as specified in
the APPEND command description. All other cases are
implementation defined.

2.3.4. [RFC-2822] Size Message Attribute

The empty string is represented number of octets in the message, as either "" (a quoted string with
zero characters between double quotes) or expressed in [RFC-2822]
format.

2.3.5. Envelope Structure Message Attribute

A parsed representation of the [RFC-2822] header of the message.
Note that the IMAP Envelope structure is not the same as {0} followed by CRLF (a
literal with an octet count
[SMTP] envelope.

2.3.6. Body Structure Message Attribute

A parsed representation of 0).

Note: Even if the octet count is 0, a client transmitting a
literal MUST wait to receive a command continuation
request. [MIME-IMB] body structure
information of the message.

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4.3.1. 8-bit and Binary Strings

8-bit textual and binary mail is supported through

2.4. Message Texts

In addition to being able to fetch the use full [RFC-2822] text of a
[MIME-IMB] content transfer encoding.
message, IMAP4rev1 implementations MAY
transmit 8-bit or multi-octet characters in literals, but SHOULD do
so only when permits the [CHARSET] fetching of portions of the full
message text. Specifically, it is identified.

Although possible to fetch the
[RFC-2822] message header, [RFC-2822] message body, a BINARY [MIME-IMB]
body encoding is defined, unencoded binary strings
are not permitted. A "binary string" is any string with NUL
characters. Implementations MUST encode binary data into part, or a textual
form such as BASE64 before transmitting [MIME-IMB] header.

3. State and Flow Diagram

Once the data. A string with an
excessive amount of CTL characters MAY also be considered to be
binary.

4.4. Parenthesized List

Data structures are represented as a "parenthesized list"; a sequence
of data items, delimited by space, connection between client and bounded at each end by
parentheses. A parenthesized list can contain other parenthesized
lists, using multiple levels server is established, an
IMAP4rev1 connection is in one of parentheses to indicate nesting. four states. The empty list initial
state is identified in the server greeting. Most commands are
only valid in certain states. It is represented as () -- a parenthesized list with no
members.

4.5. NIL

The special form "NIL" represents protocol error for the non-existence of
client to attempt a particular
data item that command while the connection is represented as in an
inappropriate state, and the server will respond with a string BAD or parenthesized list, as
distinct from
NO (depending upon server implementation) command completion
result.

3.1. Not Authenticated State

In the empty string "" or not authenticated state, the empty parenthesized list ().

Note: NIL client MUST supply
authentication credentials before most commands will be
permitted. This state is never used for any data item which takes the
form of an atom. For example, entered when a mailbox name of "NIL" connection starts
unless the connection has been pre-authenticated.

3.2. Authenticated State

In the authenticated state, the client is authenticated and MUST
select a mailbox named NIL as opposed to a non-existant mailbox
name. access before commands that affect messages
will be permitted. This state is because mailbox uses "astring" syntax which
is an atom or entered when a string. Conversely, an addr-name of NIL is
pre-authenticated connection starts, when acceptable
authentication credentials have been provided, after an error in
selecting a non-existant personal name, because addr-name uses
"nstring" syntax which is NIL mailbox, or after a string, but never an
atom. successful CLOSE command.

3.3. Selected State

In a selected state, a mailbox has been selected to access.
This state is entered when a mailbox has been successfully
selected.

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RFC 3501 IMAPv4 March 2003

5. Operational Considerations

The following rules are listed here to ensure that all IMAP4rev1
implementations interoperate properly.

5.1. Mailbox Naming

Mailbox names are 7-bit. Client implementations MUST NOT attempt to
create 8-bit mailbox names, and SHOULD interpret any 8-bit mailbox
names returned by LIST or LSUB as UTF-8. Server implementations
SHOULD prohibit

3.4. Logout State

In the creation logout state, the connection is being terminated. This
state can be entered as a result of 8-bit mailbox names, and SHOULD NOT
return 8-bit mailbox names in LIST a client request (via the
LOGOUT command) or LSUB. See section 5.1.3 for
more information by unilateral action on how to represent non-ASCII mailbox names.

Note: 8-bit mailbox names were undefined in earlier
versions the part of this protocol. Some sites used a local 8-bit
character set to represent non-ASCII mailbox names. Such
usage is not interoperable, either
the client or server.

If the client requests the logout state, the server MUST send an
untagged BYE response and is now formally deprecated.

The case-insensitive mailbox name INBOX is a special name reserved tagged OK response to
mean "the primary mailbox for this user on this server". The
interpretation of all other names is implementation-dependent.

In particular, this specification takes no position on case
sensitivity in non-INBOX mailbox names. Some the LOGOUT
command before the server implementations
are fully case-sensitive; others preserve case of a newly-created
name but otherwise are case-insensitive; closes the connection; and yet others coerce names
to a particular case. Client implementations MUST interact with any
of these. If a server implementation interprets non-INBOX mailbox
names as case-insensitive, it the client
MUST treat names using read the tagged OK response to the LOGOUT command before
the
international naming convention specially as described in section
5.1.3.

There are certain client considerations when creating a new mailbox
name:

1) Any character which is one of closes the atom-specials (see connection.

A server MUST NOT unilaterally close the Formal
Syntax) will require connection without
sending an untagged BYE response that contains the mailbox name be represented as a
quoted string or literal.

2) CTL and other non-graphic characters are difficult to represent
in a user interface and are best avoided.

3) Although reason for
having done so. A client SHOULD NOT unilaterally close the list-wildcard characters ("%"
connection, and "*") are valid
in instead SHOULD issue a mailbox name, it is difficult to use such mailbox names
with LOGOUT command. If the LIST and LSUB commands due to
server detects that the conflict with
wildcard interpretation. client has unilaterally closed the
connection, the server MAY omit the untagged BYE response and
simply close its connection.

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RFC 3501 IMAPv4 March 2003

4) Usually, a character (determined by the

+----------------------+
|connection established|
+----------------------+
||
\/
+--------------------------------------+
| server implementation)
is reserved to delimit levels of hierarchy.

5) Two characters, "#" and "&", have meanings by convention, greeting |
+--------------------------------------+
|| (1) || (2) || (3)
\/ || ||
+-----------------+ || ||
|Not Authenticated| || ||
+-----------------+ || ||
|| (7) || (4) || ||
|| \/ \/ ||
|| +----------------+ ||
|| | Authenticated |<=++ ||
|| +----------------+ || ||
|| || (7) || (5) || (6) ||
|| || \/ || ||
|| || +--------+ || ||
|| || |Selected|==++ ||
|| || +--------+ ||
|| || || (7) ||
\/ \/ \/ \/
+--------------------------------------+
| Logout |
+--------------------------------------+
||
\/
+-------------------------------+
|both sides close the connection|
+-------------------------------+

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RFC 3501 IMAPv4 March 2003

4. Data Formats

IMAP4rev1 uses textual commands and
should responses. Data in
IMAP4rev1 can be avoided except when used in one of several forms: atom, number, string,
parenthesized list, or NIL. Note that convention.

5.1.1. Mailbox Hierarchy Naming

If it is desired to export hierarchical mailbox names, mailbox names
MUST be left-to-right hierarchical using a single character to
separate levels of hierarchy. The same hierarchy separator character
is used particular data item
may take more than one form; for all levels of hierarchy within example, a single name.

5.1.2. Mailbox Namespace Naming Convention

By convention, the first hierarchical element of any mailbox name
which begins with "#" identifies data item defined as
using "astring" syntax may be either an atom or a string.

4.1. Atom

An atom consists of one or more non-special characters.

4.2. Number

A number consists of one or more digit characters, and
represents a numeric value.

4.3. String

A string is in one of two forms: either literal or quoted
string. The literal form is the "namespace" general form of string. The
quoted string form is an alternative that avoids the remainder overhead of
processing a literal at the name. This makes it possible to disambiguate between different
types cost of mailbox stores, each limitations of characters
which have their own namespaces.

For example, implementations which offer access to USENET
newsgroups MAY use the "#news" namespace to partition the
USENET newsgroup namespace from that may be used.

A literal is a sequence of other mailboxes.
Thus, zero or more octets (including CR and
LF), prefix-quoted with an octet count in the comp.mail.misc newsgroup would have form of an mailbox
name open
brace ("{"), the number of "#news.comp.mail.misc", octets, close brace ("}"), and CRLF.
In the name
"comp.mail.misc" can refer to a different object (e.g. a
user's private mailbox).

5.1.3. Mailbox International Naming Convention

By convention, international mailbox names in IMAP4rev1 are specified
using a modified version case of literals transmitted from server to client, the UTF-7 encoding described in [UTF-7].
Modified UTF-7 may also be usable in servers which implement an
earlier version of this protocol.

In modified UTF-7, printable US-ASCII characters except for "&"
represent themselves; that is, characters with octet values 0x20-0x25
and 0x27-0x7e. The character "&" (0x26)
CRLF is represented immediately followed by the
two-octet sequence "&-".

All other characters (octet values 0x00-0x1f and 0x7f-0xff) are
represented octet data. In the case of
literals transmitted from client to server, the client MUST wait
to receive a command continuation request (described later in modified BASE64, with
this document) before sending the octet data (and the remainder
of the command).

A quoted string is a further modification from
[UTF-7] that "," sequence of zero or more 7-bit characters,
excluding CR and LF, with double quote (<">) characters at each
end.

The empty string is used instead represented as either "" (a quoted string
with zero characters between double quotes) or as {0} followed
by CRLF (a literal with an octet count of "/". Modified BASE64 0).

Note: Even if the octet count is 0, a client transmitting a
literal MUST NOT be
used wait to represent any printing US-ASCII character which can represent
itself. receive a command continuation request.

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RFC 3501 IMAPv4 March 2003

"&" is used to shift to modified BASE64

4.3.1. 8-bit and "-" to shift back to
US-ASCII. There is no implicit shift from BASE64 to US-ASCII, Binary Strings

8-bit textual and
null shifts ("-&" while in BASE64; note that "&-" while binary mail is supported through the use of a
[MIME-IMB] content transfer encoding. IMAP4rev1 implementations MAY
transmit 8-bit or multi-octet characters in US-ASCII
means "&") literals, but SHOULD do
so only when the [CHARSET] is identified.

Although a BINARY body encoding is defined, unencoded binary strings
are not permitted. However, all names start in US-ASCII,
and A "binary string" is any string with NUL
characters. Implementations MUST end in US-ASCII; that is, encode binary data into a name that ends textual
form, such as BASE64, before transmitting the data. A string with an
excessive amount of CTL characters MAY also be considered to be
binary.

4.4. Parenthesized List

Data structures are represented as a non-ASCII
ISO-10646 character MUST end with "parenthesized list"; a "-").

The purpose sequence
of these modifications is data items, delimited by space, and bounded at each end by
parentheses. A parenthesized list can contain other parenthesized
lists, using multiple levels of parentheses to correct the following
problems with UTF-7:

1) UTF-7 uses the "+" character for shifting; this conflicts indicate nesting.

The empty list is represented as () -- a parenthesized list with no
members.

4.5. NIL

The special form "NIL" represents the common use non-existence of "+" in mailbox names, in a particular USENET
newsgroup names.

2) UTF-7's encoding
data item that is BASE64 which uses the "/" character; this
conflicts with the use of "/" represented as a popular hierarchy delimiter.

3) UTF-7 prohibits string or parenthesized list, as
distinct from the unencoded usage of "\"; this conflicts with empty string "" or the use of "\" as a popular hierarchy delimiter.

4) UTF-7 prohibits empty parenthesized list ().

Note: NIL is never used for any data item which takes the unencoded usage
form of "~"; this conflicts with
the use an atom. For example, a mailbox name of "~" in some servers as "NIL" is a home directory indicator.

5) UTF-7 permits multiple alternate forms
mailbox named NIL as opposed to represent the same
string; in particular, printable US-ASCII characters can be
represented in encoded form.

Although modified UTF-7 is a convention, it establishes certain
requirements on server handling of any non-existent mailbox name with
name. This is because mailbox uses "astring" syntax which
is an
embedded "&" character. In particular, server implementations
MUST preserve the exact form of the modified BASE64 portion atom or a string. Conversely, an addr-name of NIL is
a
modified UTF-7 name and treat that text as case-sensitive, even if
names are otherwise case-insensitive non-existent personal name, because addr-name uses
"nstring" syntax which is NIL or case-folded.

Server implementations SHOULD verify that any mailbox name
argument to CREATE with a string, but never an embedded "&" character is in correct
modified UTF-7 syntax; that there
atom.

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RFC 3501 IMAPv4 March 2003

5. Operational Considerations

The following rules are no superfluous shifts; and listed here to ensure that there is no encoding in modified BASE64 of any printing
US-ASCII character which can represent itself. However, client all IMAP4rev1
implementations interoperate properly.

5.1. Mailbox Naming

Mailbox names are 7-bit. Client implementations MUST NOT depend upon the server doing this; and
SHOULD NOT attempt to
create a 8-bit mailbox name with an embedded "&"
character unless it complies with modified UTF-7 syntax.

Server implementations which export a mail store which does not
follow the modified UTF-7 convention MUST convert to modified
UTF-7 names, and SHOULD interpret any 8-bit mailbox name that contains either non-ASCII characters
names returned by LIST or LSUB as UTF-8. Server implementations
SHOULD prohibit the "&" character.

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For example, here is a creation of 8-bit mailbox name which mixes English,
Chinese, names, and Japanese text:
~peter/mail/&U,BTFw-/&ZeVnLIqe-

For example, the string "&Jjo!" is not a valid mailbox
name because it does not contain SHOULD NOT
return 8-bit mailbox names in LIST or LSUB. See section 5.1.3 for
more information on how to represent non-ASCII mailbox names.

Note: 8-bit mailbox names were undefined in earlier
versions of this protocol. Some sites used a shift local 8-bit
character set to US-ASCII
before the "!". The correct form represent non-ASCII mailbox names. Such
usage is "&Jjo-!". not interoperable, and is now formally deprecated.

The
string "&U,BTFw-&ZeVnLIqe-" case-insensitive mailbox name INBOX is not permitted because it
contains a superfluous shift. special name reserved to
mean "the primary mailbox for this user on this server". The correct form
interpretation of all other names is
"&U,BTF2XlZyyKng-".

5.2. Mailbox Size implementation-dependent.

In particular, this specification takes no position on case
sensitivity in non-INBOX mailbox names. Some server implementations
are fully case-sensitive; others preserve case of a newly-created
name but otherwise are case-insensitive; and Message Status Updates

At yet others coerce names
to a particular case. Client implementations MUST interact with any time,
of these. If a server can send data that implementation interprets non-INBOX mailbox
names as case-insensitive, it MUST treat names using the
international naming convention specially as described in section
5.1.3.

There are certain client did not request.
Sometimes, such behavior is REQUIRED. For example, agents other than
the server MAY add messages to the mailbox (e.g. considerations when creating a new message
delivery), change the flags mailbox
name:

1) Any character which is one of message in the mailbox (e.g.
simultaneous access to atom-specials (see the same mailbox by multiple agents), or even
remove messages from Formal
Syntax) will require that the mailbox. A server MUST send mailbox size
updates automatically if name be represented as a mailbox size change is observed during the
processing of
quoted string or literal.

2) CTL and other non-graphic characters are difficult to represent
in a command. A server SHOULD send message flag updates
automatically, without requiring user interface and are best avoided.

3) Although the client list-wildcard characters ("%" and "*") are valid
in a mailbox name, it is difficult to request use such updates
explicitly.

Special rules exist for server notification of a client about mailbox names
with the
removal of messages LIST and LSUB commands due to prevent synchronization errors; see the
description of conflict with
wildcard interpretation.

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RFC 3501 IMAPv4 March 2003

4) Usually, a character (determined by the EXPUNGE response for more detail. In particular,
it server implementation)
is NOT permitted reserved to send an EXISTS response that would reduce the
number delimit levels of messages hierarchy.

5) Two characters, "#" and "&", have meanings by convention, and
should be avoided except when used in the mailbox; only the EXPUNGE response can do
this.

Regardless that convention.

5.1.1. Mailbox Hierarchy Naming

If it is desired to export hierarchical mailbox names, mailbox names
MUST be left-to-right hierarchical using a single character to
separate levels of what implementation decisions hierarchy. The same hierarchy separator character
is used for all levels of hierarchy within a client makes on
remembering data from single name.

5.1.2. Mailbox Namespace Naming Convention

By convention, the server, a client implementation MUST record
mailbox size updates. It MUST NOT assume that first hierarchical element of any command after
initial mailbox selection will return name
which begins with "#" identifies the size "namespace" of the mailbox.

5.3. Response when no Command in Progress

Server implementations are permitted remainder of
the name. This makes it possible to send an untagged response
(except for EXPUNGE) while there is no command in progress. Server disambiguate between different
types of mailbox stores, each of which have their own namespaces.

For example, implementations that send such responses MUST deal with flow control
considerations. Specifically, they MUST either (1) verify that which offer access to USENET
newsgroups MAY use the
size "#news" namespace to partition the
USENET newsgroup namespace from that of other mailboxes.
Thus, the data does not exceed comp.mail.misc newsgroup would have a mailbox
name of "#news.comp.mail.misc", and the underlying transport's available
window size, or (2) use non-blocking writes.

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"comp.mail.misc" can refer to a different object (e.g., a
user's private mailbox).

5.1.3. Mailbox International Naming Convention

By convention, international mailbox names in IMAP4rev1 EXPIRES 1 April 2003

5.4. Autologout Timer

If are specified
using a server has an inactivity autologout timer, modified version of the duration UTF-7 encoding described in [UTF-7].
Modified UTF-7 may also be usable in servers that implement an
earlier version of this protocol.

In modified UTF-7, printable US-ASCII characters, except for "&",
represent themselves; that
timer MUST be at least 30 minutes. is, characters with octet values 0x20-0x25
and 0x27-0x7e. The receipt of ANY command from character "&" (0x26) is represented by the client during
two-octet sequence "&-".

All other characters (octet values 0x00-0x1f and 0x7f-0xff) are
represented in modified BASE64, with a further modification from
[UTF-7] that interval SHOULD suffice "," is used instead of "/". Modified BASE64 MUST NOT be
used to reset the
autologout timer.

5.5. Multiple Commands in Progress

The client MAY send another command without waiting for the
completion result response of a command, subject represent any printing US-ASCII character which can represent
itself.

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RFC 3501 IMAPv4 March 2003

"&" is used to ambiguity rules
(see below) shift to modified BASE64 and flow control constraints on the underlying data
stream. Similarly, a server MAY begin processing another command
before processing the current command "-" to completion, subject shift back to
ambiguity rules.
US-ASCII. There is no implicit shift from BASE64 to US-ASCII, and
null shifts ("-&" while in BASE64; note that "&-" while in US-ASCII
means "&") are not permitted. However, any command continuation request responses all names start in US-ASCII,
and command continuations MUST be negotiated before any subsequent
command is initiated.

The exception is if an ambiguity would result because of end in US-ASCII; that is, a command name that would affect the results of other commands. Clients MUST NOT
send multiple commands without waiting if an ambiguity would result.
If the server detects ends with a possible ambiguity, it non-ASCII
ISO-10646 character MUST execute commands end with a "-").

The purpose of these modifications is to completion in correct the order given by following
problems with UTF-7:

1) UTF-7 uses the client.

The most obvious example "+" character for shifting; this conflicts with
the common use of ambiguity "+" in mailbox names, in particular USENET
newsgroup names.

2) UTF-7's encoding is when a command would affect BASE64 which uses the results of another command; for example, a FETCH "/" character; this
conflicts with the use of "/" as a message's
flags and popular hierarchy delimiter.

3) UTF-7 prohibits the unencoded usage of "\"; this conflicts with
the use of "\" as a STORE popular hierarchy delimiter.

4) UTF-7 prohibits the unencoded usage of that same message's flags.

A non-obvious ambiguity occurs "~"; this conflicts with commands that permit an untagged
EXPUNGE response (commands other than FETCH, STORE, and SEARCH),
since an untagged EXPUNGE response can invalidate sequence numbers
the use of "~" in some servers as a subsequent command. This home directory indicator.

5) UTF-7 permits multiple alternate forms to represent the same
string; in particular, printable US-ASCII characters can be
represented in encoded form.

Although modified UTF-7 is not a problem for FETCH, STORE, or
SEARCH commands because servers are prohibited from sending EXPUNGE
responses while convention, it establishes certain
requirements on server handling of any mailbox name with an
embedded "&" character. In particular, server implementations
MUST preserve the exact form of those commands the modified BASE64 portion of a
modified UTF-7 name and treat that text as case-sensitive, even if
names are otherwise case-insensitive or case-folded.

Server implementations SHOULD verify that any mailbox name with an
embedded "&" character, used as an argument to CREATE, is: in progress. Therefore, if the client sends
correctly modified UTF-7 syntax, has no superfluous shifts, and
has no encoding in modified BASE64 of any command other than FETCH, STORE, or SEARCH, it printing US-ASCII
character which can represent itself. However, client
implementations MUST wait for NOT depend upon the completion result response before sending server doing this, and
SHOULD NOT attempt to create a command mailbox name with message sequence numbers.

Note: UID FETCH, UID STORE, and UID SEARCH are different
commands from FETCH, STORE, and SEARCH. If the client
sends a UID command, an embedded "&"
character unless it must wait for a completion result
response before sending a command complies with message sequence
numbers.

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For example, the following non-waiting command sequences are invalid:

FETCH + NOOP + STORE
STORE + COPY + FETCH
COPY + COPY
CHECK + FETCH

The following are examples of valid non-waiting command sequences:

FETCH + STORE + SEARCH + CHECK
STORE + COPY + EXPUNGE

UID SEARCH + UID SEARCH may be valid or invalid as modified UTF-7 syntax.

Server implementations which export a non-waiting
command sequence, depending upon whether or mail store that does not
follow the second UID
SEARCH modified UTF-7 convention MUST convert to modified
UTF-7 any mailbox name that contains message sequence numbers. either non-ASCII characters
or the "&" character.

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RFC 3501 IMAPv4 March 2003

6. Client Commands

IMAP4rev1 commands are described in this section. Commands are
organized by the state in which the command

For example, here is permitted. Commands a mailbox name which are permitted in multiple states are listed in the minimum
permitted state (for example, commands valid in authenticated mixes English,
Chinese, and
selected state are listed in the authenticated state commands).

Command arguments, identified by "Arguments:" in Japanese text:
~peter/mail/&U,BTFw-/&ZeVnLIqe-

For example, the command
descriptions below, are described by function, string "&Jjo!" is not by syntax. a valid mailbox
name because it does not contain a shift to US-ASCII
before the "!". The
precise syntax of command arguments correct form is described in the Formal Syntax
section.

Some commands cause specific server responses to be returned; these
are identified by "Responses:" in the command descriptions below.
See the response descriptions in the Responses section for
information on these responses, and the Formal Syntax section for the
precise syntax of these responses. It "&Jjo-!". The
string "&U,BTFw-&ZeVnLIqe-" is possible for server data to
be transmitted as not permitted because it
contains a result of superfluous shift. The correct form is
"&U,BTF2XlZyyKng-".

5.2. Mailbox Size and Message Status Updates

At any command; thus, commands time, a server can send data that do the client did not
specifically require request.
Sometimes, such behavior is REQUIRED. For example, agents other than
the server data specify "no specific responses for
this command" instead MAY add messages to the mailbox (e.g., new message
delivery), change the flags of "none".

The "Result:" the messages in the command description refers mailbox (e.g.,
simultaneous access to the possible
tagged status responses to a command, and any special interpretation
of these status responses.

The state of a connection is only changed same mailbox by successful commands
which are documented as changing state. A rejected command (BAD
response) never changes the state of the connection multiple agents), or of even
remove messages from the
selected mailbox. A failed command (NO response) generally does not server MUST send mailbox size
updates automatically if a mailbox size change is observed during the state
processing of a command. A server SHOULD send message flag updates
automatically, without requiring the connection or client to request such updates
explicitly.

Special rules exist for server notification of a client about the selected mailbox; the
exception being the SELECT and EXAMINE commands. which

6.1. Client Commands - Any State

The following commands are valid in any state: CAPABILITY, NOOP, and
LOGOUT.

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6.1.1. CAPABILITY Command

Arguments: none

Responses: REQUIRED untagged response: CAPABILITY

Result: OK - capability completed
BAD - command unknown or arguments invalid

The CAPABILITY command requests a listing of capabilities that the
server supports. The server MUST send a single untagged
CAPABILITY response with "IMAP4rev1" as one
removal of messages to prevent synchronization errors; see the listed
capabilities before the (tagged) OK response.

A capability name which begins with "AUTH=" indicates that the
server supports that particular authentication mechanism. All
such names are, by definition, part
description of this specification. For
example, the authorization capability EXPUNGE response for more detail. In particular,
it is NOT permitted to send an experimental
"blurdybloop" authenticator EXISTS response that would be "AUTH=XBLURDYBLOOP" and not
"XAUTH=BLURDYBLOOP" or "XAUTH=XBLURDYBLOOP".

Other capability names refer to extensions, revisions, or
amendments to this specification. See reduce the documentation
number of messages in the
CAPABILITY response for additional information. No capabilities,
beyond mailbox; only the base IMAP4rev1 set defined in this specification, are
enabled without explicit EXPUNGE response can do
this.

Regardless of what implementation decisions a client action to invoke makes on
remembering data from the capability.

Client and server implementations server, a client implementation MUST implement record
mailbox size updates. It MUST NOT assume that any command after the STARTTLS,
LOGINDISABLED, and AUTH=PLAIN (described in [IMAP-TLS])
capabilities. See
initial mailbox selection will return the Security Considerations section for
important information.

See size of the section entitled "Client Commands -
Experimental/Expansion" for information about mailbox.

5.3. Response when no Command in Progress

Server implementations are permitted to send an untagged response
(except for EXPUNGE) while there is no command in progress. Server
implementations that send such responses MUST deal with flow control
considerations. Specifically, they MUST either (1) verify that the form
size of site the data does not exceed the underlying transport's available
window size, or
implementation-specific capabilities.

Example: C: abcd CAPABILITY
S: * CAPABILITY IMAP4rev1 STARTTLS AUTH=GSSAPI
LOGINDISABLED
S: abcd OK CAPABILITY completed
C: efgh STARTTLS
S: efgh OK STARTLS completed
<TLS negotiation, further commands are under [TLS] layer>
C: ijkl CAPABILITY
S: * CAPABILITY IMAP4rev1 AUTH=GSSAPI AUTH=PLAIN
S: ijkl OK CAPABILITY completed (2) use non-blocking writes.

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RFC 3501 IMAPv4 March 2003

6.1.2. NOOP Command

Arguments: none

Responses: no specific responses for this command (but see below)

Result: OK - noop completed
BAD - command unknown or arguments invalid

The NOOP command always succeeds. It does nothing.

Since any command can return a status update as untagged data, the
NOOP command can be used as a periodic poll for new messages or
message status updates during

5.4. Autologout Timer

If a period of server has an inactivity (this is autologout timer, the
preferred method to do this). duration of that
timer MUST be at least 30 minutes. The NOOP receipt of ANY command can also be used from
the client during that interval SHOULD suffice to reset any inactivity the
autologout timer on timer.

5.5. Multiple Commands in Progress

The client MAY send another command without waiting for the server.

Example: C: a002 NOOP
S: a002 OK NOOP completed
. . .
C: a047 NOOP
S: * 22 EXPUNGE
S: * 23 EXISTS
S: * 3 RECENT
S: * 14 FETCH (FLAGS (\Seen \Deleted))
S: a047 OK NOOP completed

6.1.3. LOGOUT Command

Arguments: none

Responses: REQUIRED untagged response: BYE

Result: OK - logout completed
BAD - command unknown or arguments invalid

The LOGOUT command informs
completion result response of a command, subject to ambiguity rules
(see below) and flow control constraints on the underlying data
stream. Similarly, a server that MAY begin processing another command
before processing the client current command to completion, subject to
ambiguity rules. However, any command continuation request responses
and command continuations MUST be negotiated before any subsequent
command is done with
the connection. initiated.

The server MUST send exception is if an ambiguity would result because of a BYE untagged response
before command
that would affect the (tagged) OK response, and then close results of other commands. Clients MUST NOT
send multiple commands without waiting if an ambiguity would result.
If the network
connection.

Example: C: A023 LOGOUT
S: * BYE IMAP4rev1 Server logging out
S: A023 OK LOGOUT completed
(Server and client then close server detects a possible ambiguity, it MUST execute commands
to completion in the connection)

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6.2. Client Commands - Not Authenticated State

In not authenticated state, order given by the AUTHENTICATE or LOGIN command
establishes authentication and enters authenticated state. client.

The
AUTHENTICATE most obvious example of ambiguity is when a command provides would affect
the results of another command, e.g., a general mechanism for FETCH of a variety message's flags
and a STORE of
authentication techniques, privacy protection, and integrity
checking; whereas the LOGIN command uses a traditional user name and
plaintext password pair and has no means of establishing privacy
protection or integrity checking.

The STARTTLS command is that same message's flags.

A non-obvious ambiguity occurs with commands that permit an alternate form of establishing session
privacy protection untagged
EXPUNGE response (commands other than FETCH, STORE, and integrity checking, but does not establish
authentication or enter authenticated state.

Server implementations MAY allow access to certain mailboxes without
establishing authentication. This SEARCH),
since an untagged EXPUNGE response can be done by means of the
ANONYMOUS [SASL] authenticator described invalidate sequence numbers in [ANONYMOUS]. An older
convention
a subsequent command. This is not a LOGIN command using the userid "anonymous"; problem for FETCH, STORE, or
SEARCH commands because servers are prohibited from sending EXPUNGE
responses while any of those commands are in this
case a password is required although progress. Therefore, if
the server may choose to accept client sends any password. It is implementation-dependent what restrictions are
placed on anonymous users.

Once authenticated (including as anonymous), command other than FETCH, STORE, or SEARCH, it is not possible to
re-enter not authenticated state.

In addition to
MUST wait for the universal commands (CAPABILITY, NOOP, completion result response before sending a command
with message sequence numbers.

Note: UID FETCH, UID STORE, and LOGOUT),
the following commands UID SEARCH are valid in not authenticated state:
STARTTLS, AUTHENTICATE different
commands from FETCH, STORE, and LOGIN. See SEARCH. If the Security Considerations
section client
sends a UID command, it must wait for important information about these commands.

6.2.1. STARTTLS Command

Arguments: none

Responses: no specific a completion result
response for this before sending a command

Result: OK - starttls completed, begin TLS negotiation
BAD - with message sequence
numbers.

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RFC 3501 IMAPv4 March 2003

For example, the following non-waiting command unknown sequences are invalid:

FETCH + NOOP + STORE
STORE + COPY + FETCH
COPY + COPY
CHECK + FETCH

The following are examples of valid non-waiting command sequences:

FETCH + STORE + SEARCH + CHECK
STORE + COPY + EXPUNGE

UID SEARCH + UID SEARCH may be valid or arguments invalid

A [TLS] negotiation begins immediately after as a non-waiting
command sequence, depending upon whether or not the CRLF at second UID
SEARCH contains message sequence numbers.

6. Client Commands

IMAP4rev1 commands are described in this section. Commands are
organized by the end
of state in which the tagged OK response from command is permitted. Commands
which are permitted in multiple states are listed in the server. Once a client issues a
STARTTLS command, it MUST NOT issue further minimum
permitted state (for example, commands until a
server response is seen valid in authenticated and
selected state are listed in the [TLS] negotiation is complete.

The server remains authenticated state commands).

Command arguments, identified by "Arguments:" in non-authenticated state, even if client
credentials are supplied during the [TLS] negotiation. This does command
descriptions below, are described by function, not preclude an authentication mechanism such as EXTERNAL (defined by syntax. The
precise syntax of command arguments is described in [SASL]) from using client identity determined the Formal Syntax
section.

Some commands cause specific server responses to be returned; these
are identified by "Responses:" in the [TLS]

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negotiation.

Once [TLS] has been started, command descriptions below.
See the client MUST discard cached response descriptions in the Responses section for
information about server capabilities on these responses, and SHOULD re-issue the
CAPABILITY command. This Formal Syntax section for the
precise syntax of these responses. It is necessary possible for server data to protect against man-in-
the-middle attacks which alter
be transmitted as a result of any command. Thus, commands that do
not specifically require server data specify "no specific responses
for this command" instead of "none".

The "Result:" in the capabilities list prior command description refers to
STARTTLS. the possible
tagged status responses to a command, and any special interpretation
of these status responses.

The server MAY advertise different capabilities after
STARTTLS.

Example: C: a001 CAPABILITY
S: * CAPABILITY IMAP4rev1 STARTTLS LOGINDISABLED
S: a001 OK CAPABILITY completed
C: a002 STARTTLS
S: a002 OK Begin TLS negotiation now
<TLS negotiation, further state of a connection is only changed by successful commands
which are under [TLS] layer>
C: a003 CAPABILITY
S: * CAPABILITY IMAP4rev1 AUTH=PLAIN
S: a003 OK CAPABILITY completed
C: a004 LOGIN joe password
S: a004 OK LOGIN completed

6.2.2. AUTHENTICATE Command

Arguments: authentication mechanism name

Responses: continuation data can be requested

Result: OK - authenticate completed, now in authenticated state
NO - authenticate failure: unsupported authentication
mechanism, credentials documented as changing state. A rejected
BAD - command unknown or arguments invalid,
authentication exchange cancelled

The AUTHENTICATE command indicates a [SASL] authentication
mechanism to (BAD
response) never changes the server. If state of the server supports connection or of the requested
authentication mechanism, it performs an authentication protocol
exchange to authenticate and identify the client. It MAY also
negotiate an OPTIONAL security layer for subsequent protocol
interactions. If the requested authentication mechanism is not
supported, the server SHOULD reject the AUTHENTICATE command by
sending a tagged NO response.

The AUTHENTICATE
selected mailbox. A failed command (NO response) generally does not support
change the optional "initial
response" feature state of [SASL]. Section 5.1 the connection or of [SASL] specifies how
to handle an authentication mechanism which uses an initial
response. the selected mailbox; the
exception being the SELECT and EXAMINE commands.

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RFC 3501 IMAPv4 March 2003

6.1. Client Commands - Any State

The service name specified by this protocol's profile of [SASL] is
"imap". following commands are valid in any state: CAPABILITY, NOOP, and
LOGOUT.

6.1.1. CAPABILITY Command

Arguments: none

Responses: REQUIRED untagged response: CAPABILITY

Result: OK - capability completed
BAD - command unknown or arguments invalid

The authentication protocol exchange consists of CAPABILITY command requests a series listing of
server challenges and client responses capabilities that are specific to the
authentication mechanism. A
server challenge consists of a
command continuation request response with the "+" token followed
by a BASE64 encoded string. supports. The client response consists of server MUST send a single line consisting untagged
CAPABILITY response with "IMAP4rev1" as one of a BASE64 encoded string. If the client
wishes to cancel an authentication exchange, it issues a line
consisting of a single "*". If listed
capabilities before the (tagged) OK response.

A capability name which begins with "AUTH=" indicates that the
server receives supports that particular authentication mechanism. All
such an
response, it MUST reject the AUTHENTICATE command names are, by sending a
tagged BAD response.

If a security layer is negotiated through the [SASL]
authentication exchange, it takes effect immediately following the
CRLF that concludes definition, part of this specification. For
example, the authentication exchange authorization capability for the client, an experimental
"blurdybloop" authenticator would be "AUTH=XBLURDYBLOOP" and not
"XAUTH=BLURDYBLOOP" or "XAUTH=XBLURDYBLOOP".

Other capability names refer to extensions, revisions, or
amendments to this specification. See the CRLF documentation of the tagged OK
CAPABILITY response for additional information. No capabilities,
beyond the server.

While client and server implementations MUST implement the
AUTHENTICATE command itself, it is not required to implement any
authentication mechanisms other than the PLAIN mechanism described base IMAP4rev1 set defined in [IMAP-TLS]. Also, an authentication mechanism is not required this specification, are
enabled without explicit client action to support any security layers.

Note: a server implementation MUST implement a
configuration in which it does NOT permit any plaintext
password mechanisms, unless either the STARTTLS command
has been negotiated or some other mechanism that
protects invoke the session from password snooping has been
provided. Server sites SHOULD NOT use any configuration
which permits a plaintext password mechanism without
such a protection mechanism against password snooping. capability.

Client and server implementations SHOULD MUST implement
additional [SASL] mechanisms which do not use plaintext
passwords, such the GSSAPI mechanism described in [SASL]
and/or the [DIGEST-MD5] mechanism.

Servers STARTTLS,
LOGINDISABLED, and clients can support multiple authentication
mechanisms. The server SHOULD list its supported authentication
mechanisms AUTH=PLAIN (described in [IMAP-TLS])
capabilities. See the response to Security Considerations section for
important information.

See the CAPABILITY command so that section entitled "Client Commands -
Experimental/Expansion" for information about the
client knows which authentication mechanisms to use.

A server MAY include a CAPABILITY response code in the tagged OK
response form of a successful AUTHENTICATE command in order to send
capabilities automatically. It is unnecessary for a client to
send a separate CAPABILITY command if it recognizes these
automatic site or
implementation-specific capabilities. This should only be done if a security

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RFC 3501 IMAPv4 March 2003

layer was not negotiated by the AUTHENTICATE command, because the
tagged OK response as part of an AUTHENTICATE command is not
protected by encryption/integrity checking. [SASL] requires the
client to re-issue a CAPABILITY command in this case.

If an AUTHENTICATE command fails with a NO response, the client
MAY try another authentication mechanism by issuing another
AUTHENTICATE command. It MAY also attempt to authenticate by
using the LOGIN command (see section 6.2.3 for more detail). In
other words, the client MAY request authentication types in
decreasing order of preference, with the LOGIN command as a last
resort.

The authorization identity passed from the client to the server
during the authentication exchange is interpreted by the server as
the user name whose privileges the client is requesting.

Example: C: abcd CAPABILITY
S: * OK CAPABILITY IMAP4rev1 Server
C: A001 AUTHENTICATE GSSAPI STARTTLS AUTH=GSSAPI
LOGINDISABLED
S: + abcd OK CAPABILITY completed
C: YIIB+wYJKoZIhvcSAQICAQBuggHqMIIB5qADAgEFoQMCAQ6iBw
MFACAAAACjggEmYYIBIjCCAR6gAwIBBaESGxB1Lndhc2hpbmd0
b24uZWR1oi0wK6ADAgEDoSQwIhsEaW1hcBsac2hpdmFtcy5jYW
Mud2FzaGluZ3Rvbi5lZHWjgdMwgdCgAwIBAaEDAgEDooHDBIHA
cS1GSa5b+fXnPZNmXB9SjL8Ollj2SKyb+3S0iXMljen/jNkpJX
AleKTz6BQPzj8duz8EtoOuNfKgweViyn/9B9bccy1uuAE2HI0y
C/PHXNNU9ZrBziJ8Lm0tTNc98kUpjXnHZhsMcz5Mx2GR6dGknb
I0iaGcRerMUsWOuBmKKKRmVMMdR9T3EZdpqsBd7jZCNMWotjhi
vd5zovQlFqQ2Wjc2+y46vKP/iXxWIuQJuDiisyXF0Y8+5GTpAL
pHDc1/pIGmMIGjoAMCAQGigZsEgZg2on5mSuxoDHEA1w9bcW9n
FdFxDKpdrQhVGVRDIzcCMCTzvUboqb5KjY1NJKJsfjRQiBYBdE
NKfzK+g5DlV8nrw81uOcP8NOQCLR5XkoMHC0Dr/80ziQzbNqhx
O6652Npft0LQwJvenwDI13YxpwOdMXzkWZN/XrEqOWp6GCgXTB
vCyLWLlWnbaUkZdEYbKHBPjd8t/1x5Yg== efgh STARTTLS
S: + YGgGCSqGSIb3EgECAgIAb1kwV6ADAgEFoQMCAQ+iSzBJoAMC
AQGiQgRAtHTEuOP2BXb9sBYFR4SJlDZxmg39IxmRBOhXRKdDA0
uHTCOT9Bq3OsUTXUlk0CsFLoa8j+gvGDlgHuqzWHPSQg== efgh OK STARTLS completed
<TLS negotiation, further commands are under [TLS] layer>
C: ijkl CAPABILITY
S: + YDMGCSqGSIb3EgECAgIBAAD/////6jcyG4GE3KkTzBeBiVHe
ceP2CWY0SR0fAQAgAAQEBAQ=
C: YDMGCSqGSIb3EgECAgIBAAD/////3LQBHXTpFfZgrejpLlLImP
wkhbfa2QteAQAgAG1yYwE= * CAPABILITY IMAP4rev1 AUTH=GSSAPI AUTH=PLAIN
S: A001 ijkl OK GSSAPI authentication successful

Note: The line breaks in the first client response are for
editorial clarity and are not in real authenticators.

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6.2.3. LOGIN CAPABILITY completed

6.1.2. NOOP Command

Arguments: user name
password none

Responses: no specific responses for this command (but see below)

Result: OK - login completed, now in authenticated state
NO - login failure: user name or password rejected noop completed
BAD - command unknown or arguments invalid

The LOGIN NOOP command identifies the client to the server and carries
the plaintext password authenticating this user.

A server MAY include always succeeds. It does nothing.

Since any command can return a CAPABILITY response code in status update as untagged data, the tagged OK
response to a successful LOGIN
NOOP command in order to send
capabilities automatically. It is unnecessary can be used as a periodic poll for new messages or
message status updates during a client period of inactivity (this is the
preferred method to
send a separate CAPABILITY do this). The NOOP command if it recognizes these
automatic capabilities. can also be used
to reset any inactivity autologout timer on the server.

Example: C: a001 LOGIN SMITH SESAME a002 NOOP
S: a001 a002 OK LOGIN NOOP completed

Note: Use of the LOGIN
. . .
C: a047 NOOP
S: * 22 EXPUNGE
S: * 23 EXISTS
S: * 3 RECENT
S: * 14 FETCH (FLAGS (\Seen \Deleted))
S: a047 OK NOOP completed

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RFC 3501 IMAPv4 March 2003

6.1.3. LOGOUT Command

Arguments: none

Responses: REQUIRED untagged response: BYE

Result: OK - logout completed
BAD - command over an insecure network
(such as unknown or arguments invalid

The LOGOUT command informs the Internet) server that the client is a security risk, because anyone
monitoring network traffic can obtain plaintext passwords.
The LOGIN command SHOULD NOT be used except as a last
resort, and it is recommended that client implementations
have a means to disable any automatic use of done with
the LOGIN
command.

A connection. The server implementation MUST implement send a configuration in
which, unless either the STARTTLS command has been
negotiated or some other mechanism that protects the
session from password snooping has been provided, it
advertises BYE untagged response
before the LOGINDISABLED capability (tagged) OK response, and does NOT permit then close the LOGIN command. network
connection.

Example: C: A023 LOGOUT
S: * BYE IMAP4rev1 Server sites SHOULD NOT use any
configuration which permits the LOGIN command without such
a protection mechanism against password snooping. A logging out
S: A023 OK LOGOUT completed
(Server and client
implementation MUST NOT send a LOGIN command if then close the
LOGINDISABLED capability is advertised.

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6.3. connection)

6.2. Client Commands - Not Authenticated State

In the not authenticated state, commands that manipulate mailboxes as atomic
entities are permitted. Of these commands, the SELECT AUTHENTICATE or LOGIN command
establishes authentication and EXAMINE
commands will select enters the authenticated state. The
AUTHENTICATE command provides a mailbox general mechanism for access a variety of
authentication techniques, privacy protection, and enter selected state.

In addition to integrity
checking; whereas the universal commands (CAPABILITY, NOOP, LOGIN command uses a traditional user name and LOGOUT),
plaintext password pair and has no means of establishing privacy
protection or integrity checking.

The STARTTLS command is an alternate form of establishing session
privacy protection and integrity checking, but does not establish
authentication or enter the following commands are valid in authenticated state.

Server implementations MAY allow access to certain mailboxes without
establishing authentication. This can be done by means of the
ANONYMOUS [SASL] authenticator described in [ANONYMOUS]. An older
convention is a LOGIN command using the userid "anonymous"; in this
case, a password is required although the server may choose to accept
any password. The restrictions placed on anonymous users are
implementation-dependent.

Once authenticated (including as anonymous), it is not possible to
re-enter not authenticated state.

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RFC 3501 IMAPv4 March 2003

In addition to the universal commands (CAPABILITY, NOOP, and LOGOUT),
the following commands are valid in the not authenticated state: SELECT,
EXAMINE, CREATE, DELETE, RENAME, SUBSCRIBE, UNSUBSCRIBE, LIST, LSUB,
STATUS,
STARTTLS, AUTHENTICATE and APPEND.

6.3.1. SELECT LOGIN. See the Security Considerations
section for important information about these commands.

6.2.1. STARTTLS Command

Arguments: mailbox name none

Responses: REQUIRED untagged responses: FLAGS, EXISTS, RECENT
REQUIRED OK untagged responses: UNSEEN, PERMANENTFLAGS,
UIDNEXT, UIDVALIDITY no specific response for this command

Result: OK - select starttls completed, now in selected state
NO - select failure, now in authenticated state: no
such mailbox, can't access mailbox begin TLS negotiation
BAD - command unknown or arguments invalid

The SELECT command selects a mailbox so that messages in

A [TLS] negotiation begins immediately after the
mailbox can be accessed. Before returning an CRLF at the end
of the tagged OK to response from the client, server. Once a client issues a
STARTTLS command, it MUST NOT issue further commands until a
server response is seen and the [TLS] negotiation is complete.

The server MUST send remains in the following untagged data to non-authenticated state, even if client
credentials are supplied during the client.
Note that earlier versions of this protocol only required the
FLAGS, EXISTS, and RECENT untagged data; consequently, client
implementations SHOULD implement default behavior for missing data [TLS] negotiation. This does
not preclude an authentication mechanism such as discussed with the individual item.

FLAGS Defined flags in the mailbox. See the description
of the FLAGS response for more detail.

<n> EXISTS The number of messages in the mailbox. See the
description of the EXISTS response for more detail.

<n> RECENT The number of messages with the \Recent flag set.
See the description of the RECENT response for more
detail.

OK [UNSEEN <n>]
The message sequence number of the first unseen
message EXTERNAL (defined
in [SASL]) from using client identity determined by the mailbox. If this is missing, [TLS]
negotiation.

Once [TLS] has been started, the client can not make any assumptions MUST discard cached
information about the first
unseen message in the mailbox, server capabilities and needs to issue a
SEARCH command if it wants to find it.

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OK [PERMANENTFLAGS (<list of flags>)]
A list of message flags that SHOULD re-issue the client can change
permanently. If this
CAPABILITY command. This is missing, the client should
assume that all flags can be changed permanently.

OK [UIDNEXT <n>]
The next unique identifier value. Refer necessary to section
2.3.1.1 for more information. If this is missing,
the client can not make any assumptions about protect against man-in-
the-middle attacks which alter the
next unique identifier value.

OK [UIDVALIDITY <n>]
The unique identifier validity value. Refer capabilities list prior to
section 2.3.1.1 for more information. If this is
missing, the
STARTTLS. The server does not support unique
identifiers.

Only one mailbox MAY advertise different capabilities after
STARTTLS.

Example: C: a001 CAPABILITY
S: * CAPABILITY IMAP4rev1 STARTTLS LOGINDISABLED
S: a001 OK CAPABILITY completed
C: a002 STARTTLS
S: a002 OK Begin TLS negotiation now
<TLS negotiation, further commands are under [TLS] layer>
C: a003 CAPABILITY
S: * CAPABILITY IMAP4rev1 AUTH=PLAIN
S: a003 OK CAPABILITY completed
C: a004 LOGIN joe password
S: a004 OK LOGIN completed

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RFC 3501 IMAPv4 March 2003

6.2.2. AUTHENTICATE Command

Arguments: authentication mechanism name

Responses: continuation data can be selected at a time requested

Result: OK - authenticate completed, now in a connection;
simultaneous access to multiple mailboxes requires multiple
connections. authenticated state
NO - authenticate failure: unsupported authentication
mechanism, credentials rejected
BAD - command unknown or arguments invalid,
authentication exchange cancelled

The SELECT AUTHENTICATE command automatically deselects any
currently selected mailbox before attempting the new selection.
Consequently, if a mailbox is selected and indicates a SELECT command that
fails is attempted, no mailbox is selected.

If the client is permitted [SASL] authentication
mechanism to modify the mailbox, server. If the server
SHOULD prefix the text of supports the tagged OK response with requested
authentication mechanism, it performs an authentication protocol
exchange to authenticate and identify the
"[READ-WRITE]" response code. client. It MAY also
negotiate an OPTIONAL security layer for subsequent protocol
interactions. If the client requested authentication mechanism is not permitted to modify the mailbox but is
permitted read access, the mailbox is selected as read-only, and
supported, the server MUST prefix the text of SHOULD reject the AUTHENTICATE command by
sending a tagged OK response to
SELECT with the "[READ-ONLY]" response code. Read-only access
through SELECT differs from the EXAMINE NO response.

The AUTHENTICATE command in that certain
read-only mailboxes MAY permit does not support the change optional "initial
response" feature of permanent state on a
per-user (as opposed [SASL]. Section 5.1 of [SASL] specifies how
to global) basis. Netnews messages marked in
a server-based .newsrc file are handle an example authentication mechanism which uses an initial
response.

The service name specified by this protocol's profile of such per-user
permanent state that can be modified with read-only mailboxes.

Example: C: A142 SELECT INBOX
S: * 172 EXISTS
S: * 1 RECENT
S: * OK [UNSEEN 12] Message 12 [SASL] is first unseen
S: * OK [UIDVALIDITY 3857529045] UIDs valid
S: * OK [UIDNEXT 4392] Predicted next UID
S: * FLAGS (\Answered \Flagged \Deleted \Seen \Draft)
S: * OK [PERMANENTFLAGS (\Deleted \Seen \*)] Limited
S: A142 OK [READ-WRITE] SELECT completed

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6.3.2. EXAMINE Command

Arguments: mailbox name

Responses: REQUIRED untagged responses: FLAGS, EXISTS, RECENT
REQUIRED OK untagged responses: UNSEEN, PERMANENTFLAGS,
UIDNEXT, UIDVALIDITY

Result: OK - examine completed, now in selected state
NO - examine failure, now in authenticated state: no
such mailbox, can't access mailbox
BAD - command unknown or arguments invalid
"imap".

The EXAMINE command is identical to SELECT authentication protocol exchange consists of a series of
server challenges and returns the same
output; however, the selected mailbox is identified as read-only.
No changes client responses that are specific to the permanent state
authentication mechanism. A server challenge consists of a
command continuation request response with the mailbox, including
per-user state, are permitted; in particular, EXAMINE MUST NOT
cause messages to lose the \Recent flag. "+" token followed
by a BASE64 encoded string. The text client response consists of a
single line consisting of a BASE64 encoded string. If the tagged OK response client
wishes to cancel an authentication exchange, it issues a line
consisting of a single "*". If the EXAMINE command server receives such a
response, it MUST
begin with reject the "[READ-ONLY]" response code.

Example: C: A932 EXAMINE blurdybloop
S: * 17 EXISTS
S: * 2 RECENT
S: * OK [UNSEEN 8] Message 8 is first unseen
S: * OK [UIDVALIDITY 3857529045] UIDs valid
S: * OK [UIDNEXT 4392] Predicted next UID
S: * FLAGS (\Answered \Flagged \Deleted \Seen \Draft)
S: * OK [PERMANENTFLAGS ()] No permanent flags permitted
S: A932 OK [READ-ONLY] EXAMINE completed

6.3.3. CREATE Command

Arguments: mailbox name

Responses: no specific responses for this command

Result: OK - create completed
NO - create failure: can't create mailbox with that name
BAD - command unknown or arguments invalid

The CREATE AUTHENTICATE command creates a mailbox with the given name. An OK
response is returned only if a new mailbox with that name has been
created. It is an error to attempt to create INBOX or a mailbox
with a name that refers to an extant mailbox. Any error in
creation will return by sending a
tagged NO BAD response.

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If the mailbox name is suffixed with the server's hierarchy
separator character (as returned from the server by a LIST
command), this security layer is a declaration that negotiated through the client intends to create
mailbox names under this name in the hierarchy. Server
implementations that do not require this declaration MUST ignore
the declaration. In any case, [SASL]
authentication exchange, it takes effect immediately following the name
CRLF that is created is concludes the
name without authentication exchange for the trailing hierarchy delimiter.

If client,
and the server's hierarchy separator character appears elsewhere in CRLF of the name, tagged OK response for the server.

While client and server SHOULD create any superior hierarchical names
that are needed for implementations MUST implement the CREATE
AUTHENTICATE command itself, it is not required to complete successfully.
In implement any
authentication mechanisms other words, than the PLAIN mechanism described

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RFC 3501 IMAPv4 March 2003

in [IMAP-TLS]. Also, an attempt authentication mechanism is not required
to create "foo/bar/zap" on support any security layers.

Note: a server implementation MUST implement a
configuration in which "/" is it does NOT permit any plaintext
password mechanisms, unless either the hierarchy separator character STARTTLS command
has been negotiated or some other mechanism that
protects the session from password snooping has been
provided. Server sites SHOULD create foo/ NOT use any configuration
which permits a plaintext password mechanism without
such a protection mechanism against password snooping.
Client and foo/bar/ if they server implementations SHOULD implement
additional [SASL] mechanisms that do not already exist.

If a new mailbox is created with use plaintext
passwords, such the same name as a mailbox which
was deleted, GSSAPI mechanism described in [SASL]
and/or the [DIGEST-MD5] mechanism.

Servers and clients can support multiple authentication
mechanisms. The server SHOULD list its unique identifiers MUST be greater than any
unique identifiers used supported authentication
mechanisms in the previous incarnation of response to the mailbox
UNLESS CAPABILITY command so that the new incarnation has
client knows which authentication mechanisms to use.

A server MAY include a different unique identifier
validity value. See the description of CAPABILITY response code in the UID command for more
detail.

Example: C: A003 CREATE owatagusiam/
S: A003 OK CREATE completed
C: A004 CREATE owatagusiam/blurdybloop
S: A004 tagged OK CREATE completed

Note: The interpretation of this example depends on whether
"/" was returned as the hierarchy separator from LIST. If
"/" is the hierarchy separator, a new level
response of hierarchy
named "owatagusiam" with a member called "blurdybloop" successful AUTHENTICATE command in order to send
capabilities automatically. It is
created. Otherwise, two mailboxes at the same hierarchy
level are created.

6.3.4. DELETE Command

Arguments: mailbox name

Responses: no specific responses unnecessary for this command

Result: OK - delete completed
NO - delete failure: can't delete mailbox with that name
BAD - command unknown or arguments invalid

The DELETE a client to
send a separate CAPABILITY command permanently removes if it recognizes these
automatic capabilities. This should only be done if a security
layer was not negotiated by the mailbox with AUTHENTICATE command, because the given
name. A
tagged OK response as part of an AUTHENTICATE command is returned only if not
protected by encryption/integrity checking. [SASL] requires the mailbox has
been deleted. It is an error to attempt
client to delete INBOX or re-issue a

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mailbox name that does not exist.

The DELETE CAPABILITY command MUST NOT remove inferior hierarchical names.
For example, if a mailbox "foo" has in this case.

If an inferior "foo.bar"
(assuming "." is the hierarchy delimiter character), removing
"foo" MUST NOT remove "foo.bar". AUTHENTICATE command fails with a NO response, the client
MAY try another authentication mechanism by issuing another
AUTHENTICATE command. It is an error to MAY also attempt to
delete a name that has inferior hierarchical names and also has authenticate by
using the \Noselect mailbox name attribute LOGIN command (see the description of the
LIST response section 6.2.3 for more details).

It is permitted to delete a name that has inferior hierarchical
names and does not have the \Noselect mailbox name attribute. detail). In
this case, all messages in that mailbox are removed, and the name
will acquire the \Noselect mailbox name attribute.

The value of
other words, the highest-used unique identifier client MAY request authentication types in
decreasing order of preference, with the deleted
mailbox MUST be preserved so that LOGIN command as a new mailbox created with last
resort.

The authorization identity passed from the
same name will not reuse client to the identifiers of server
during the former
incarnation, UNLESS authentication exchange is interpreted by the new incarnation has a different unique
identifier validity value. See server as
the description of user name whose privileges the UID command
for more detail.

Examples: C: A682 LIST "" * client is requesting.

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RFC 3501 IMAPv4 March 2003

Example: S: * LIST () "/" blurdybloop OK IMAP4rev1 Server
C: A001 AUTHENTICATE GSSAPI
S: * LIST (\Noselect) "/" foo +
C: YIIB+wYJKoZIhvcSAQICAQBuggHqMIIB5qADAgEFoQMCAQ6iBw
MFACAAAACjggEmYYIBIjCCAR6gAwIBBaESGxB1Lndhc2hpbmd0
b24uZWR1oi0wK6ADAgEDoSQwIhsEaW1hcBsac2hpdmFtcy5jYW
Mud2FzaGluZ3Rvbi5lZHWjgdMwgdCgAwIBAaEDAgEDooHDBIHA
cS1GSa5b+fXnPZNmXB9SjL8Ollj2SKyb+3S0iXMljen/jNkpJX
AleKTz6BQPzj8duz8EtoOuNfKgweViyn/9B9bccy1uuAE2HI0y
C/PHXNNU9ZrBziJ8Lm0tTNc98kUpjXnHZhsMcz5Mx2GR6dGknb
I0iaGcRerMUsWOuBmKKKRmVMMdR9T3EZdpqsBd7jZCNMWotjhi
vd5zovQlFqQ2Wjc2+y46vKP/iXxWIuQJuDiisyXF0Y8+5GTpAL
pHDc1/pIGmMIGjoAMCAQGigZsEgZg2on5mSuxoDHEA1w9bcW9n
FdFxDKpdrQhVGVRDIzcCMCTzvUboqb5KjY1NJKJsfjRQiBYBdE
NKfzK+g5DlV8nrw81uOcP8NOQCLR5XkoMHC0Dr/80ziQzbNqhx
O6652Npft0LQwJvenwDI13YxpwOdMXzkWZN/XrEqOWp6GCgXTB
vCyLWLlWnbaUkZdEYbKHBPjd8t/1x5Yg==
S: * LIST () "/" foo/bar + YGgGCSqGSIb3EgECAgIAb1kwV6ADAgEFoQMCAQ+iSzBJoAMC
AQGiQgRAtHTEuOP2BXb9sBYFR4SJlDZxmg39IxmRBOhXRKdDA0
uHTCOT9Bq3OsUTXUlk0CsFLoa8j+gvGDlgHuqzWHPSQg==
C:
S: A682 OK LIST completed + YDMGCSqGSIb3EgECAgIBAAD/////6jcyG4GE3KkTzBeBiVHe
ceP2CWY0SR0fAQAgAAQEBAQ=
C: A683 DELETE blurdybloop YDMGCSqGSIb3EgECAgIBAAD/////3LQBHXTpFfZgrejpLlLImP
wkhbfa2QteAQAgAG1yYwE=
S: A683 A001 OK DELETE completed
C: A684 DELETE foo
S: A684 NO Name "foo" has inferior hierarchical names
C: A685 DELETE foo/bar
S: A685 OK DELETE Completed
C: A686 LIST "" *
S: * LIST (\Noselect) "/" foo
S: A686 OK LIST completed
C: A687 DELETE foo
S: A687 OK DELETE Completed

C: A82 LIST "" *
S: * LIST () "." blurdybloop
S: * LIST () "." foo
S: * LIST () "." foo.bar
S: A82 OK LIST completed
C: A83 DELETE blurdybloop
S: A83 OK DELETE completed
C: A84 DELETE foo

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S: A84 OK DELETE Completed
C: A85 LIST "" *
S: * LIST () "." foo.bar
S: A85 OK LIST completed
C: A86 LIST "" %
S: * LIST (\Noselect) "." foo
S: A86 OK LIST completed

6.3.5. RENAME GSSAPI authentication successful

Note: The line breaks within server challenges and client
responses are for editorial clarity and are not in real
authenticators.

6.2.3. LOGIN Command

Arguments: existing mailbox name
new mailbox user name
password

Responses: no specific responses for this command

Result: OK - rename completed login completed, now in authenticated state
NO - rename login failure: can't rename mailbox with that name,
can't rename to mailbox with that user name or password rejected
BAD - command unknown or arguments invalid

The RENAME LOGIN command changes identifies the name of a mailbox. client to the server and carries
the plaintext password authenticating this user.

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RFC 3501 IMAPv4 March 2003

A server MAY include a CAPABILITY response code in the tagged OK
response is returned only if the mailbox has been renamed. to a successful LOGIN command in order to send
capabilities automatically. It is
an error unnecessary for a client to attempt to rename from a mailbox name that does not
exist or to a mailbox name that already exists. Any error in
renaming will return
send a tagged NO response.

If separate CAPABILITY command if it recognizes these
automatic capabilities.

Example: C: a001 LOGIN SMITH SESAME
S: a001 OK LOGIN completed

Note: Use of the name has inferior hierarchical names, then LOGIN command over an insecure network
(such as the inferior
hierarchical names MUST also Internet) is a security risk, because anyone
monitoring network traffic can obtain plaintext passwords.
The LOGIN command SHOULD NOT be renamed. For example, used except as a rename of
"foo" to "zap" will rename "foo/bar" (assuming "/" last
resort, and it is the
hierarchy delimiter character) recommended that client implementations
have a means to "zap/bar".

If the server's hierarchy separator character appears in the name,
the server SHOULD create disable any superior hierarchical names that are
needed for automatic use of the RENAME LOGIN
command.

Unless either the STARTTLS command to complete successfully. In has been negotiated or
some other
words, an attempt to rename "foo/bar/zap" to baz/rag/zowie on mechanism that protects the session from
password snooping has been provided, a server
implementation MUST implement a configuration in which "/" is it
advertises the hierarchy separator character SHOULD
create baz/ LOGINDISABLED capability and baz/rag/ if they do not already exist.

The value of does NOT permit
the highest-used unique identifier of LOGIN command. Server sites SHOULD NOT use any
configuration which permits the old mailbox
name LOGIN command without such
a protection mechanism against password snooping. A client
implementation MUST be preserved so that NOT send a new mailbox created with the same
name LOGIN command if the
LOGINDISABLED capability is advertised.

6.3. Client Commands - Authenticated State

In the authenticated state, commands that manipulate mailboxes as
atomic entities are permitted. Of these commands, the SELECT and
EXAMINE commands will not reuse select a mailbox for access and enter the identifiers of
selected state.

In addition to the former incarnation,
UNLESS universal commands (CAPABILITY, NOOP, and LOGOUT),
the new incarnation has following commands are valid in the authenticated state: SELECT,
EXAMINE, CREATE, DELETE, RENAME, SUBSCRIBE, UNSUBSCRIBE, LIST, LSUB,
STATUS, and APPEND.

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RFC 3501 IMAPv4 March 2003

6.3.1. SELECT Command

Arguments: mailbox name

Responses: REQUIRED untagged responses: FLAGS, EXISTS, RECENT
REQUIRED OK untagged responses: UNSEEN, PERMANENTFLAGS,
UIDNEXT, UIDVALIDITY

Result: OK - select completed, now in selected state
NO - select failure, now in authenticated state: no
such mailbox, can't access mailbox
BAD - command unknown or arguments invalid

The SELECT command selects a different unique identifier
validity value. mailbox so that messages in the
mailbox can be accessed. Before returning an OK to the client,
the server MUST send the following untagged data to the client.
Note that earlier versions of this protocol only required the
FLAGS, EXISTS, and RECENT untagged data; consequently, client
implementations SHOULD implement default behavior for missing data
as discussed with the individual item.

FLAGS Defined flags in the mailbox. See the description
of the UID command FLAGS response for more detail.

Renaming INBOX is permitted, and has special behavior. It moves
all

<n> EXISTS The number of messages in INBOX to a new mailbox with the given name,

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leaving INBOX empty. If the server implementation supports
inferior hierarchical names of INBOX, these are unaffected by a
rename mailbox. See the
description of INBOX.

Examples: C: A682 LIST "" *
S: * LIST () "/" blurdybloop
S: * LIST (\Noselect) "/" foo
S: * LIST () "/" foo/bar
S: A682 OK LIST completed
C: A683 RENAME blurdybloop sarasoop
S: A683 OK RENAME completed
C: A684 RENAME foo zowie
S: A684 OK RENAME Completed
C: A685 LIST "" *
S: * LIST () "/" sarasoop
S: * LIST (\Noselect) "/" zowie
S: * LIST () "/" zowie/bar
S: A685 OK LIST completed

C: Z432 LIST "" *
S: * LIST () "." INBOX
S: * LIST () "." INBOX.bar
S: Z432 OK LIST completed
C: Z433 RENAME INBOX old-mail
S: Z433 OK RENAME completed
C: Z434 LIST "" *
S: * LIST () "." INBOX
S: * LIST () "." INBOX.bar
S: * LIST () "." old-mail
S: Z434 OK LIST completed

6.3.6. SUBSCRIBE Command

Arguments: mailbox

Responses: no specific responses the EXISTS response for this command

Result: OK - subscribe completed
NO - subscribe failure: can't subscribe to that name
BAD - command unknown or arguments invalid more detail.

<n> RECENT The SUBSCRIBE command adds number of messages with the specified mailbox name to \Recent flag set.
See the
server's set description of "active" or "subscribed" mailboxes as returned by the LSUB command. This command returns a tagged OK RECENT response only
if for more
detail.

OK [UNSEEN <n>]
The message sequence number of the subscription first unseen
message in the mailbox. If this is successful.

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A server MAY validate missing, the mailbox argument to SUBSCRIBE
client can not make any assumptions about the first
unseen message in the mailbox, and needs to verify
that it exists. However, issue a
SEARCH command if it MUST NOT unilaterally remove an
existing mailbox name from the subscription wants to find it.

OK [PERMANENTFLAGS (<list of flags>)]
A list even if a mailbox
by of message flags that name no longer exists.

Note: This requirement the client can change
permanently. If this is because a server site missing, the client should
assume that all flags can
choose be changed permanently.

OK [UIDNEXT <n>]
The next unique identifier value. Refer to routinely remove a mailbox with a well-known
name (e.g. "system-alerts") after its contents expire,
with section
2.3.1.1 for more information. If this is missing,
the intention of recreating it when new contents
are appropriate.

Example: C: A002 SUBSCRIBE #news.comp.mail.mime
S: A002 client can not make any assumptions about the
next unique identifier value.

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OK SUBSCRIBE completed

6.3.7. UNSUBSCRIBE Command

Arguments: mailbox name

Responses: no specific responses [UIDVALIDITY <n>]
The unique identifier validity value. Refer to
section 2.3.1.1 for more information. If this command

Result: OK - unsubscribe completed
NO - unsubscribe failure: can't unsubscribe that name
BAD - command unknown or arguments invalid is
missing, the server does not support unique
identifiers.

Only one mailbox can be selected at a time in a connection;
simultaneous access to multiple mailboxes requires multiple
connections. The UNSUBSCRIBE SELECT command removes the specified automatically deselects any
currently selected mailbox name from before attempting the server's set of "active" or "subscribed" mailboxes as returned
by the LSUB command. This command returns new selection.
Consequently, if a mailbox is selected and a SELECT command that
fails is attempted, no mailbox is selected.

If the client is permitted to modify the mailbox, the server
SHOULD prefix the text of the tagged OK response
only if with the unsubscription
"[READ-WRITE]" response code.

If the client is successful. not permitted to modify the mailbox but is
permitted read access, the mailbox is selected as read-only, and
the server MUST prefix the text of the tagged OK response to
SELECT with the "[READ-ONLY]" response code. Read-only access
through SELECT differs from the EXAMINE command in that certain
read-only mailboxes MAY permit the change of permanent state on a
per-user (as opposed to global) basis. Netnews messages marked in
a server-based .newsrc file are an example of such per-user
permanent state that can be modified with read-only mailboxes.

Example: C: A002 UNSUBSCRIBE #news.comp.mail.mime A142 SELECT INBOX
S: A002 * 172 EXISTS
S: * 1 RECENT
S: * OK UNSUBSCRIBE [UNSEEN 12] Message 12 is first unseen
S: * OK [UIDVALIDITY 3857529045] UIDs valid
S: * OK [UIDNEXT 4392] Predicted next UID
S: * FLAGS (\Answered \Flagged \Deleted \Seen \Draft)
S: * OK [PERMANENTFLAGS (\Deleted \Seen \*)] Limited
S: A142 OK [READ-WRITE] SELECT completed

6.3.8. LIST

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6.3.2. EXAMINE Command

Arguments: reference name mailbox name with possible wildcards

Responses: REQUIRED untagged responses: LIST FLAGS, EXISTS, RECENT
REQUIRED OK untagged responses: UNSEEN, PERMANENTFLAGS,
UIDNEXT, UIDVALIDITY

Result: OK - list completed examine completed, now in selected state
NO - list failure: examine failure, now in authenticated state: no
such mailbox, can't list that reference or name access mailbox
BAD - command unknown or arguments invalid

The LIST EXAMINE command returns a subset of names from the complete set
of all names available is identical to the client. Zero or more untagged LIST

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replies are returned, containing the name attributes, hierarchy
delimiter, SELECT and name; see the description of returns the LIST reply for
more detail.

The LIST command SHOULD return its data quickly, without undue
delay. For example, it SHOULD NOT go to excess trouble to
calculate \Marked or \Unmarked status or perform other processing;
if each name requires 1 second of processing, then a list of 1200
names would take 20 minutes!

An empty ("" string) reference name argument indicates that same
output; however, the selected mailbox name is interpreted identified as by SELECT. The returned mailbox
names MUST match the supplied mailbox name pattern. A non-empty
reference name argument is the name of a mailbox or a level of
mailbox hierarchy, and indicates the context in which the mailbox
name is interpreted.

An empty ("" string) mailbox name argument is a special request read-only.
No changes to
return the hierarchy delimiter and the root name permanent state of the name given mailbox, including
per-user state, are permitted; in particular, EXAMINE MUST NOT
cause messages to lose the reference. \Recent flag.

The value returned as text of the root MAY be tagged OK response to the empty
string if EXAMINE command MUST
begin with the reference is non-rooted or "[READ-ONLY]" response code.

Example: C: A932 EXAMINE blurdybloop
S: * 17 EXISTS
S: * 2 RECENT
S: * OK [UNSEEN 8] Message 8 is the empty string. In
all cases, a hierarchy delimiter (or NIL if there is no hierarchy)
is returned. This permits a client to get the hierarchy delimiter
(or find out that the first unseen
S: * OK [UIDVALIDITY 3857529045] UIDs valid
S: * OK [UIDNEXT 4392] Predicted next UID
S: * FLAGS (\Answered \Flagged \Deleted \Seen \Draft)
S: * OK [PERMANENTFLAGS ()] No permanent flags permitted
S: A932 OK [READ-ONLY] EXAMINE completed

6.3.3. CREATE Command

Arguments: mailbox names are flat) even when name

Responses: no
mailboxes by specific responses for this command

Result: OK - create completed
NO - create failure: can't create mailbox with that name currently exist.
BAD - command unknown or arguments invalid

The reference and CREATE command creates a mailbox name arguments are interpreted into with the given name. An OK
response is returned only if a
canonical form new mailbox with that represents name has been
created. It is an unambiguous left-to-right
hierarchy. The returned error to attempt to create INBOX or a mailbox names will be
with a name that refers to an extant mailbox. Any error in
creation will return a tagged NO response.

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RFC 3501 IMAPv4 March 2003

If the interpreted
form.

Note: The interpretation of the reference argument mailbox name is
implementation-defined. It depends upon whether suffixed with the
server implementation has a concept of "current working
directory" and leading "break out characters" which
override server's hierarchy
separator character (as returned from the current working directory.

For example, on a server which exports by a UNIX or NT
filesystems, the reference argument contains the current
working directory and LIST
command), this is a declaration that the client intends to create
mailbox names under this name argument would
contain in the hierarchy. Server
implementations that do not require this declaration MUST ignore
the declaration. In any case, the name as interpreted in created is without the current working
directory.
trailing hierarchy delimiter.

If a server implementation has no concept of break out
characters, the canonical form is normally server's hierarchy separator character appears elsewhere in
the reference
name appended with name, the mailbox name. Note server SHOULD create any superior hierarchical names
that if are needed for the CREATE command to be successfully
completed. In other words, an attempt to create "foo/bar/zap" on
a server implements the namespace convention (section
5.1.2), "#" in which "/" is a break out the hierarchy separator character SHOULD
create foo/ and must be treated

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as such.

If the reference argument is foo/bar/ if they do not already exist.

If a level of new mailbox
hierarchy (that is, it is a \NoInferiors name), and/or
the reference argument does not end created with the hierarchy
delimiter, it is implementation-dependent how this is
interpreted. For example, a reference of "foo/bar" and
mailbox same name of "rag/baz" could be interpreted as
"foo/bar/rag/baz", "foo/barrag/baz", or "foo/rag/baz".
A client SHOULD NOT use such a reference argument except
at the explicit request of the user. A hierarchical
browser mailbox which
was deleted, its unique identifiers MUST NOT make be greater than any assumptions about server
interpretation
unique identifiers used in the previous incarnation of the reference unless mailbox
UNLESS the reference is new incarnation has a level of mailbox hierarchy AND ends with different unique identifier
validity value. See the hierarchy
delimiter.

Any part description of the reference argument that is included in the
interpreted form SHOULD prefix the interpreted form. It SHOULD
also be in the same form UID command for more
detail.

Example: C: A003 CREATE owatagusiam/
S: A003 OK CREATE completed
C: A004 CREATE owatagusiam/blurdybloop
S: A004 OK CREATE completed

Note: The interpretation of this example depends on whether
"/" was returned as the reference name argument. This
rule permits the client to determine if the returned mailbox name hierarchy separator from LIST. If
"/" is in the context hierarchy separator, a new level of hierarchy
named "owatagusiam" with a member called "blurdybloop" is
created. Otherwise, two mailboxes at the reference argument, same hierarchy
level are created.

6.3.4. DELETE Command

Arguments: mailbox name

Responses: no specific responses for this command

Result: OK - delete completed
NO - delete failure: can't delete mailbox with that name
BAD - command unknown or if something about arguments invalid

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The DELETE command permanently removes the mailbox argument overrode with the reference argument. Without
this rule, given
name. A tagged OK response is returned only if the client would have mailbox has
been deleted. It is an error to have knowledge of the server's
naming semantics including what characters are "breakouts" that
override attempt to delete INBOX or a naming context.
mailbox name that does not exist.

The DELETE command MUST NOT remove inferior hierarchical names.
For example, here are some examples of how references
and if a mailbox names might be interpreted on "foo" has an inferior "foo.bar"
(assuming "." is the hierarchy delimiter character), removing
"foo" MUST NOT remove "foo.bar". It is an error to attempt to
delete a UNIX-based
server:

Reference Mailbox Name Interpretation
------------ ------------ --------------
~smith/Mail/ foo.* ~smith/Mail/foo.*
archive/ % archive/%
#news. comp.mail.* #news.comp.mail.*
~smith/Mail/ /usr/doc/foo /usr/doc/foo
archive/ ~fred/Mail/* ~fred/Mail/*

The first three examples demonstrate interpretations in
the context of the reference argument. Note that
"~smith/Mail" SHOULD NOT be transformed into something
like "/u2/users/smith/Mail", or it would be impossible
for the client to determine name that the interpretation was
in the context of the reference.

The character "*" is a wildcard, has inferior hierarchical names and matches zero or more
characters at this position. The character "%" is similar to "*",
but it does not match a hierarchy delimiter. If the "%" wildcard

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is the last character of a mailbox name argument, matching levels
of hierarchy are also returned. If these levels of hierarchy are
not also selectable mailboxes, they are returned with has
the \Noselect mailbox name attribute (see the description of the
LIST response for more details).

Server implementations are

It is permitted to "hide" otherwise
accessible mailboxes from the wildcard characters, by preventing
certain characters or names from matching a wildcard in certain
situations. For example, delete a UNIX-based server might restrict the
interpretation of "*" so name that an initial "/" character has inferior hierarchical
names and does not
match.

The special name INBOX is included in have the output from LIST, if
INBOX is supported by this server for \Noselect mailbox name attribute. In
this user case, all messages in that mailbox are removed, and if the
uppercase string "INBOX" matches name
will acquire the interpreted reference and \Noselect mailbox name arguments with wildcards as described above. attribute.

The
criteria for omitting INBOX is whether SELECT INBOX will return
failure; it is not relevant whether value of the user's real INBOX resides
on this or some other server.

Example: highest-used unique identifier of the deleted
mailbox MUST be preserved so that a new mailbox created with the
same name will not reuse the identifiers of the former
incarnation, UNLESS the new incarnation has a different unique
identifier validity value. See the description of the UID command
for more detail.

Examples: C: A101 A682 LIST "" "" *
S: * LIST () "/" blurdybloop
S: * LIST (\Noselect) "/" "" foo
S: A101 * LIST () "/" foo/bar
S: A682 OK LIST completed
C: A683 DELETE blurdybloop
S: A683 OK DELETE completed
C: A684 DELETE foo
S: A684 NO Name "foo" has inferior hierarchical names
C: A685 DELETE foo/bar
S: A685 OK DELETE Completed
C: A102 A686 LIST #news.comp.mail.misc "" *
S: * LIST (\Noselect) "." #news. "/" foo
S: A102 A686 OK LIST completed
C: A687 DELETE foo
S: A687 OK DELETE Completed

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C: A103 A82 LIST /usr/staff/jones "" *
S: * LIST (\Noselect) "/" / () "." blurdybloop
S: A103 * LIST () "." foo
S: * LIST () "." foo.bar
S: A82 OK LIST completed
C: A83 DELETE blurdybloop
S: A83 OK DELETE completed
C: A84 DELETE foo
S: A84 OK DELETE Completed
C: A202 A85 LIST ~/Mail/ % "" *
S: * LIST (\Noselect) "/" ~/Mail/foo () "." foo.bar
S: A85 OK LIST completed
C: A86 LIST "" %
S: * LIST () "/" ~/Mail/meetings (\Noselect) "." foo
S: A202 A86 OK LIST completed

6.3.9. LSUB

6.3.5. RENAME Command

Arguments: reference existing mailbox name
new mailbox name with possible wildcards

Responses: untagged responses: LSUB no specific responses for this command

Result: OK - lsub rename completed
NO - lsub rename failure: can't list rename mailbox with that name,
can't rename to mailbox with that reference or name
BAD - command unknown or arguments invalid

The LSUB RENAME command returns changes the name of a subset of names from the set of names

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that mailbox. A tagged OK
response is returned only if the user mailbox has declared as being "active" or "subscribed".
Zero been renamed. It is
an error to attempt to rename from a mailbox name that does not
exist or more untagged LSUB replies are returned. The arguments to
LSUB are in the same form as those for LIST.

The returned untagged LSUB response MAY contain different a mailbox
flags from name that already exists. Any error in
renaming will return a LIST untagged tagged NO response.

If this should happen, the
flags in the untagged LIST are considered more authoritative.

A special situation occurs when using LSUB with name has inferior hierarchical names, then the % wildcard.
Consider what happens if "foo/bar" (with inferior
hierarchical names MUST also be renamed. For example, a hierarchy delimiter rename of
"/") is subscribed but
"foo" to "zap" will rename "foo/bar" (assuming "/" is not. A "%" wildcard the
hierarchy delimiter character) to LSUB must
return foo, not foo/bar, "zap/bar".

If the server's hierarchy separator character appears in the LSUB response, and it MUST be
flagged with name,
the \Noselect attribute.

The server MUST NOT unilaterally remove SHOULD create any superior hierarchical names that are
needed for the RENAME command to complete successfully. In other
words, an existing mailbox name
from attempt to rename "foo/bar/zap" to baz/rag/zowie on a
server in which "/" is the subscription list even hierarchy separator character SHOULD
create baz/ and baz/rag/ if a mailbox by that name no
longer exists.

Example: C: A002 LSUB "#news." "comp.mail.*"
S: * LSUB () "." #news.comp.mail.mime
S: * LSUB () "." #news.comp.mail.misc
S: A002 OK LSUB completed
C: A003 LSUB "#news." "comp.%"
S: * LSUB (\NoSelect) "." #news.comp.mail
S: A003 OK LSUB completed

6.3.10. STATUS Command

Arguments: mailbox name
status data item names

Responses: untagged responses: STATUS

Result: OK - status completed
NO - status failure: no status for that name
BAD - command unknown or arguments invalid they do not already exist.

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The STATUS command requests the status value of the indicated mailbox.
It does not change the currently selected mailbox, nor does it
affect the state highest-used unique identifier of any messages in the queried old mailbox (in
particular, STATUS
name MUST NOT cause messages to lose the \Recent
flag).

The STATUS command provides an alternative to opening a second
IMAP4rev1 connection and doing an EXAMINE command on be preserved so that a new mailbox to
query that mailbox's status without deselecting created with the current
mailbox in same
name will not reuse the first IMAP4rev1 connection.

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Unlike identifiers of the LIST command, former incarnation,
UNLESS the STATUS new incarnation has a different unique identifier
validity value. See the description of the UID command for more
detail.

Renaming INBOX is not guaranteed to
be fast permitted, and has special behavior. It moves
all messages in its response. Under certain circumstances, it can be
quite slow. In some implementations, the server is obliged INBOX to
open the a new mailbox read-only internally to obtain certain status
information. Also unlike with the LIST command, given name,
leaving INBOX empty. If the STATUS command
does not accept wildcards.

Note: The STATUS command is intended to access
information mailboxes other than the currently selected
mailbox. Because the STATUS command can cause the
mailbox to be opened internally, and because this
information is available server implementation supports
inferior hierarchical names of INBOX, these are unaffected by other means on the selected
mailbox, the STATUS command SHOULD NOT be used on the
currently selected mailbox.

The STATUS command MUST NOT be used as a "check for new
messages in the selected mailbox" operation (refer to
sections 7, 7.3.1, and 7.3.2 for more information about
the proper method for new message checking).

Because the STATUS command is not guaranteed to be fast
in its results, clients SHOULD NOT expect to be able to
issue many consecutive STATUS commands and obtain
reasonable performance.

The currently defined status data items that can be requested are:

MESSAGES
The number of messages in the mailbox.

RECENT
The number of messages with the \Recent flag set.

UIDNEXT
The next unique identifier value of the mailbox. Refer to
section 2.3.1.1 for more information.

UIDVALIDITY
The unique identifier validity value of the mailbox. Refer to
section 2.3.1.1 for more information.

UNSEEN
The number
rename of messages which do not have the \Seen flag set.

Example: INBOX.

Examples: C: A042 STATUS A682 LIST "" *
S: * LIST () "/" blurdybloop (UIDNEXT MESSAGES)
S: * STATUS LIST (\Noselect) "/" foo
S: * LIST () "/" foo/bar
S: A682 OK LIST completed
C: A683 RENAME blurdybloop (MESSAGES 231 UIDNEXT 44292) sarasoop
S: A042 A683 OK STATUS RENAME completed

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6.3.11. APPEND Command

Arguments:
C: A684 RENAME foo zowie
S: A684 OK RENAME Completed
C: A685 LIST "" *
S: * LIST () "/" sarasoop
S: * LIST (\Noselect) "/" zowie
S: * LIST () "/" zowie/bar
S: A685 OK LIST completed

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6.3.6. SUBSCRIBE Command

Arguments: mailbox name
OPTIONAL flag parenthesized list
OPTIONAL date/time string
message literal

Responses: no specific responses for this command

Result: OK - append subscribe completed
NO - append error: subscribe failure: can't append subscribe to that mailbox, error
in flags or date/time or message text name
BAD - command unknown or arguments invalid

The APPEND SUBSCRIBE command appends adds the literal argument as a new message specified mailbox name to the end
server's set of "active" or "subscribed" mailboxes as returned by
the specified destination mailbox. LSUB command. This argument
SHOULD be in the format of an [RFC-2822] message. 8-bit
characters are permitted in command returns a tagged OK response only
if the message. subscription is successful.

A server implementation
that is unable to preserve 8-bit data properly MUST be able to
reversibly convert 8-bit APPEND data to 7-bit using a [MIME-IMB]
content transfer encoding.

Note: There MAY be exceptions, e.g. draft messages, in
which required [RFC-2822] header lines are omitted in validate the message literal mailbox argument to APPEND. The full
implications of doing so SUBSCRIBE to verify
that it exists. However, it MUST be understood and
carefully weighed.

If a flag parenthesized list is specified, the flags SHOULD be set
in the resulting message; otherwise, NOT unilaterally remove an
existing mailbox name from the flag subscription list of the
resulting message is set empty by default. In either case, the
Recent flag is also set.

If even if a date-time is specified, the internal date SHOULD be set in
the resulting message; otherwise, the internal date of the
resulting message is set to the current date and time by default.

If the append is unsuccessful for any reason, the mailbox MUST be
restored to its state before the APPEND attempt;
by that name no partial
appending longer exists.

Note: This requirement is permitted.

If the destination mailbox does not exist, because a server MUST return an
error, and MUST NOT automatically create site can
choose to routinely remove a mailbox with a well-known
name (e.g., "system-alerts") after its contents expire,
with the mailbox. Unless intention of recreating it
is certain when new contents
are appropriate.

Example: C: A002 SUBSCRIBE #news.comp.mail.mime
S: A002 OK SUBSCRIBE completed

6.3.7. UNSUBSCRIBE Command

Arguments: mailbox name

Responses: no specific responses for this command

Result: OK - unsubscribe completed
NO - unsubscribe failure: can't unsubscribe that name
BAD - command unknown or arguments invalid

The UNSUBSCRIBE command removes the destination specified mailbox can not be created, the
server MUST send the response code "[TRYCREATE]" as the prefix of name from
the text server's set of "active" or "subscribed" mailboxes as returned
by the tagged NO response. LSUB command. This gives command returns a hint to tagged OK response
only if the
client that it can attempt a CREATE command and retry the APPEND
if the CREATE unsubscription is successful.

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If the mailbox is currently selected, the normal new message
actions SHOULD occur. Specifically, the server SHOULD notify the
client immediately via an untagged EXISTS response. If the server
does not do so, the client MAY issue a NOOP command (or failing
that, a CHECK command) after one or more APPEND commands.

Example: C: A003 APPEND saved-messages (\Seen) {310}
S: + Ready for literal data
C: Date: Mon, 7 Feb 1994 21:52:25 -0800 (PST)
C: From: Fred Foobar <foobar@Blurdybloop.COM>
C: Subject: afternoon meeting
C: To: mooch@owatagu.siam.edu
C: Message-Id: <B27397-0100000@Blurdybloop.COM>
C: MIME-Version: 1.0
C: Content-Type: TEXT/PLAIN; CHARSET=US-ASCII
C:
C: Hello Joe, do you think we can meet at 3:30 tomorrow?
C: A002 UNSUBSCRIBE #news.comp.mail.mime
S: A003 A002 OK APPEND UNSUBSCRIBE completed

Note: The APPEND command is not used for message delivery,
because it does not provide a mechanism to transfer [SMTP]
envelope information.

6.4. Client Commands - Selected State

In selected state, commands that manipulate messages in a mailbox are
permitted.

In addition to the universal commands (CAPABILITY, NOOP, and LOGOUT),
and the authenticated state commands (SELECT, EXAMINE, CREATE,
DELETE, RENAME, SUBSCRIBE, UNSUBSCRIBE, LIST, LSUB, STATUS, and
APPEND), the following commands are valid in the selected state:
CHECK, CLOSE, EXPUNGE, SEARCH, FETCH, STORE, COPY, and UID.

6.4.1. CHECK

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RFC 3501 IMAPv4 March 2003

6.3.8. LIST Command

Arguments: none reference name
mailbox name with possible wildcards

Responses: no specific responses for this command untagged responses: LIST

Result: OK - check list completed
NO - list failure: can't list that reference or name
BAD - command unknown or arguments invalid

The CHECK LIST command requests returns a checkpoint subset of names from the currently selected
mailbox. A checkpoint refers complete set
of all names available to any implementation-dependent
housekeeping associated with the mailbox (e.g. resolving client. Zero or more untagged LIST
replies are returned, containing the

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server's in-memory state of name attributes, hierarchy
delimiter, and name; see the mailbox with description of the state on LIST reply for
more detail.

The LIST command SHOULD return its
disk) data quickly, without undue
delay. For example, it SHOULD NOT go to excess trouble to
calculate the \Marked or \Unmarked status or perform other
processing; if each name requires 1 second of processing, then a
list of 1200 names would take 20 minutes!

An empty ("" string) reference name argument indicates that the
mailbox name is not normally executed interpreted as part of each command. by SELECT. The returned mailbox
names MUST match the supplied mailbox name pattern. A
checkpoint MAY take a non-instantaneous amount non-empty
reference name argument is the name of real time to
complete. If a server implementation has no such housekeeping
considerations, CHECK is equivalent to NOOP.

There is no guarantee that an EXISTS untagged response will happen
as mailbox or a result level of CHECK. NOOP, not CHECK, SHOULD be used for new
message polling.

Example: C: FXXZ CHECK
S: FXXZ OK CHECK Completed

6.4.2. CLOSE Command

Arguments: none

Responses: no specific responses for this command

Result: OK - close completed, now
mailbox hierarchy, and indicates the context in authenticated state
BAD - command unknown or arguments invalid

The CLOSE command permanently removes from which the currently selected mailbox all messages that have the \Deleted flag set, and returns
name is interpreted.

An empty ("" string) mailbox name argument is a special request to authenticated state from selected state. No untagged EXPUNGE
responses are sent.

No messages are removed,
return the hierarchy delimiter and no error is given, the root name of the name given
in the reference. The value returned as the root MAY be the empty
string if the mailbox reference is
selected by an EXAMINE command non-rooted or is otherwise selected read-only.

Even if an empty string. In
all cases, a mailbox hierarchy delimiter (or NIL if there is selected, a SELECT, EXAMINE, or LOGOUT
command MAY be issued without previously issuing no hierarchy)
is returned. This permits a CLOSE command.
The SELECT, EXAMINE, and LOGOUT commands implicitly close client to get the hierarchy delimiter
(or find out that the
currently selected mailbox without doing an expunge. However, names are flat) even when many messages no
mailboxes by that name currently exist.

The reference and mailbox name arguments are deleted, interpreted into a CLOSE-LOGOUT or CLOSE-SELECT
sequence is considerably faster than
canonical form that represents an EXPUNGE-LOGOUT or
EXPUNGE-SELECT because no untagged EXPUNGE responses (which unambiguous left-to-right
hierarchy. The returned mailbox names will be in the
client would probably ignore) are sent.

Example: C: A341 CLOSE
S: A341 OK CLOSE completed interpreted
form.

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RFC 3501 IMAPv4 March 2003

6.4.3. EXPUNGE Command

Arguments: none

Responses: untagged responses: EXPUNGE

Result: OK - expunge completed
NO - expunge failure: can't expunge (e.g. permission
denied)
BAD - command unknown or arguments invalid

Note: The EXPUNGE command permanently removes from interpretation of the currently
selected mailbox all messages that have reference argument is
implementation-defined. It depends upon whether the \Deleted flag set.
Before returning an OK to
server implementation has a concept of the client, an untagged EXPUNGE response
is sent for each message that is removed.

Example: C: A202 EXPUNGE
S: * 3 EXPUNGE
S: * 3 EXPUNGE
S: * 5 EXPUNGE
S: * 8 EXPUNGE
S: A202 OK EXPUNGE completed

Note: In this example, messages 3, 4, 7, "current
working directory" and 11 had leading "break out characters",
which override the
\Deleted flag set. See current working directory.

For example, on a server which exports a UNIX or NT
filesystem, the description of reference argument contains the EXPUNGE
response for further explanation.

6.4.4. SEARCH Command

Arguments: OPTIONAL [CHARSET] specification
searching criteria (one or more)

Responses: REQUIRED untagged response: SEARCH

Result: OK - search completed
NO - search error: can't search that [CHARSET] or
criteria
BAD - command unknown or arguments invalid

The SEARCH command searches current
working directory, and the mailbox for messages that match name argument would
contain the given searching criteria. Searching criteria consist of one
or more search keys. The untagged SEARCH response from name as interpreted in the server
contains current working
directory.

If a listing server implementation has no concept of message sequence numbers corresponding to
those messages that match the searching criteria.

When multiple keys are specified, break out
characters, the result canonical form is normally the intersection
(AND function) of all reference
name appended with the messages mailbox name. Note that match those keys. For

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example, if the criteria DELETED FROM "SMITH" SINCE 1-Feb-1994 refers
to all deleted messages from Smith that were placed in
server implements the mailbox
since February 1, 1994. A search key can also namespace convention (section
5.1.2), "#" is a break out character and must be treated
as such.

If the reference argument is not a parenthesized
list level of one or more search keys (e.g. for use mailbox
hierarchy (that is, it is a \NoInferiors name), and/or
the reference argument does not end with the OR hierarchy
delimiter, it is implementation-dependent how this is
interpreted. For example, a reference of "foo/bar" and
mailbox name of "rag/baz" could be interpreted as
"foo/bar/rag/baz", "foo/barrag/baz", or "foo/rag/baz".
A client SHOULD NOT
keys).

Server implementations MAY exclude [MIME-IMB] body parts with
terminal content media types other than TEXT and MESSAGE from
consideration in SEARCH matching.

The OPTIONAL [CHARSET] specification consists use such a reference argument except
at the explicit request of the word
"CHARSET" followed by user. A hierarchical
browser MUST NOT make any assumptions about server
interpretation of the reference unless the reference is
a registered [CHARSET]. It indicates level of mailbox hierarchy AND ends with the
[CHARSET] hierarchy
delimiter.

Any part of the strings reference argument that appear is included in the search criteria.
[MIME-IMB] content transfer encodings, and [MIME-HDRS] strings in
[RFC-2822]/[MIME-IMB] headers, MUST
interpreted form SHOULD prefix the interpreted form. It SHOULD
also be decoded before comparing
text in a [CHARSET] other than US-ASCII. US-ASCII MUST be
supported; other [CHARSET]s MAY be supported.

If the server does not support same form as the specified [CHARSET], it MUST
return a tagged NO response (not a BAD). reference name argument. This response SHOULD
contain the BADCHARSET response code, which MAY list
rule permits the
[CHARSET]s supported by the server.

In all search keys that use strings, a message matches the key client to determine if the string is a substring of the field. The matching returned mailbox name
is
case-insensitive.

The defined search keys are as follows. Refer to the Formal
Syntax section for in the precise syntactic definitions context of the
arguments.

<sequence set>
Messages with message sequence numbers corresponding to reference argument, or if something about
the
specified message sequence number set

ALL
All messages in mailbox argument overrode the mailbox; reference argument. Without
this rule, the default initial key for
ANDing.

ANSWERED
Messages with client would have to have knowledge of the \Answered flag set.

BCC <string>
Messages server's
naming semantics including what characters are "breakouts" that contain the specified string in the envelope
structure's BCC field.

BEFORE <date>
Messages whose internal date (disregarding time and timezone)
override a naming context.

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RFC 3501 IMAPv4 March 2003

is earlier than the specified date.

BODY <string>
Messages that contain the specified string

For example, here are some examples of how references
and mailbox names might be interpreted on a UNIX-based
server:

The first three examples demonstrate interpretations in
the body context of the
message.

CC <string>
Messages reference argument. Note that contain
"~smith/Mail" SHOULD NOT be transformed into something
like "/u2/users/smith/Mail", or it would be impossible
for the specified string in client to determine that the envelope
structure's CC field.

DELETED
Messages with interpretation was
in the \Deleted flag set.

DRAFT
Messages with context of the \Draft flag set.

FLAGGED
Messages with the \Flagged flag set.

FROM <string>
Messages that contain the specified string in the envelope
structure's FROM field.

HEADER <field-name> <string>
Messages that have reference.

The character "*" is a header with the specified field-name (as
defined in [RFC-2822]) wildcard, and that contains the specified string
in the text of the header (what comes after the colon). matches zero or more
characters at this position. The character "%" is similar to "*",
but it does not match a hierarchy delimiter. If the
string to search "%" wildcard
is zero-length, this matches all messages that
have a header line with the specified field-name regardless last character of
the contents.

KEYWORD <flag>
Messages a mailbox name argument, matching levels
of hierarchy are also returned. If these levels of hierarchy are
not also selectable mailboxes, they are returned with the specified keyword flag set.

LARGER <n>
Messages with an [RFC-2822] size larger than
\Noselect mailbox name attribute (see the specified
number description of octets.

NEW
Messages that have the \Recent flag set but not the \Seen flag.
This is functionally equivalent LIST
response for more details).

Server implementations are permitted to "(RECENT UNSEEN)".

NOT <search-key>
Messages that do not match "hide" otherwise
accessible mailboxes from the specified search key.

OLD
Messages wildcard characters, by preventing
certain characters or names from matching a wildcard in certain
situations. For example, a UNIX-based server might restrict the
interpretation of "*" so that do an initial "/" character does not have
match.

The special name INBOX is included in the \Recent flag set. This output from LIST, if
INBOX is
functionally equivalent to "NOT RECENT" (as opposed to "NOT

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NEW").

ON <date>
Messages whose internal date (disregarding time and timezone)
is within the specified date.

OR <search-key1> <search-key2>
Messages that match either search key.

RECENT
Messages that have the \Recent flag set.

SEEN
Messages that have the \Seen flag set.

SENTBEFORE <date>
Messages whose [RFC-2822] Date: header (disregarding time supported by this server for this user and
timezone) is earlier than if the specified date.

SENTON <date>
Messages whose [RFC-2822] Date: header (disregarding time and
timezone) is within
uppercase string "INBOX" matches the specified date.

SENTSINCE <date>
Messages whose [RFC-2822] Date: header (disregarding time interpreted reference and
timezone)
mailbox name arguments with wildcards as described above. The
criteria for omitting INBOX is within or later than the specified date.

SINCE <date>
Messages whose internal date (disregarding time and timezone) whether SELECT INBOX will return
failure; it is within or later than the specified date.

SMALLER <n>
Messages with an [RFC-2822] size smaller than the specified
number of octets.

SUBJECT <string>
Messages that contain the specified string in the envelope
structure's SUBJECT field.

TEXT <string>
Messages that contain the specified string in not relevant whether the header user's real INBOX resides
on this or
body of the message.

TO <string>
Messages that contain the specified string in the envelope some other server.

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RFC 3501 IMAPv4 March 2003

structure's TO field.

UID <sequence set>
Messages with unique identifiers corresponding to the specified
unique identifier set. Sequence set ranges are permitted.

UNANSWERED
Messages that do not have the \Answered flag set.

UNDELETED
Messages that do not have the \Deleted flag set.

UNDRAFT
Messages that do not have the \Draft flag set.

UNFLAGGED
Messages that do not have the \Flagged flag set.

UNKEYWORD <flag>
Messages that do not have the specified keyword flag set.

UNSEEN
Messages that do not have the \Seen flag set.

Example: C: A282 SEARCH FLAGGED SINCE 1-Feb-1994 NOT FROM "Smith" A101 LIST "" ""
S: * SEARCH 2 84 882 LIST (\Noselect) "/" ""
S: A282 A101 OK SEARCH completed LIST Completed
C: A283 SEARCH TEXT "string not in mailbox" A102 LIST #news.comp.mail.misc ""
S: * SEARCH LIST (\Noselect) "." #news.
S: A283 A102 OK SEARCH completed LIST Completed
C: A103 LIST /usr/staff/jones ""
S: A284 SEARCH CHARSET UTF-8 TEXT {6}
XXXXXX * LIST (\Noselect) "/" /
S: A103 OK LIST Completed
C: A202 LIST ~/Mail/ %
S: * SEARCH 43 LIST (\Noselect) "/" ~/Mail/foo
S: A284 * LIST () "/" ~/Mail/meetings
S: A202 OK SEARCH LIST completed

Note: Since this document is restricted to 7-bit ASCII
text, it is not possible to show actual UTF-8 data. The
"XXXXXX" is a placeholder for what would be 6 octets of
8-bit data in an actual transaction.

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6.4.5. FETCH

6.3.9. LSUB Command

Arguments: sequence set
message data item names or macro reference name
mailbox name with possible wildcards

Responses: untagged responses: FETCH LSUB

Result: OK - fetch lsub completed
NO - fetch error: lsub failure: can't fetch list that data reference or name
BAD - command unknown or arguments invalid

The FETCH LSUB command retrieves data associated with returns a message in subset of names from the
mailbox. set of names
that the user has declared as being "active" or "subscribed".
Zero or more untagged LSUB replies are returned. The data items arguments to be fetched can be either a single atom
or a parenthesized list.

Most data items, identified in the formal syntax under the
msg-att-static rule,
LSUB are static and MUST NOT change for any
particular message. Other data items, identified in the formal
syntax under the msg-att-dynamic rule, MAY change, either same form as a
result of a STORE command or due to external events.

For example, if a client receives an ENVELOPE those for LIST.

The returned untagged LSUB response MAY contain different mailbox
flags from a
message when it already knows LIST untagged response. If this should happen, the envelope, it can
safely ignore
flags in the newly transmitted envelope.

There untagged LIST are three macros which specify commonly-used sets of data
items, and can be used instead considered more authoritative.

A special situation occurs when using LSUB with the % wildcard.
Consider what happens if "foo/bar" (with a hierarchy delimiter of data items.
"/") is subscribed but "foo" is not. A macro "%" wildcard to LSUB must be
used by itself, and
return foo, not foo/bar, in conjunction with other macros or data
items.

ALL
Macro equivalent to: (FLAGS INTERNALDATE RFC822.SIZE ENVELOPE)

FAST
Macro equivalent to: (FLAGS INTERNALDATE RFC822.SIZE)

FULL
Macro equivalent to: (FLAGS INTERNALDATE RFC822.SIZE ENVELOPE
BODY)

The currently defined data items that can the LSUB response, and it MUST be fetched are:

BODY
Non-extensible form of BODYSTRUCTURE.

BODY[<section>]<<partial>>
The text of a particular body section.
flagged with the \Noselect attribute.

The section
specification is server MUST NOT unilaterally remove an existing mailbox name
from the subscription list even if a set of zero or more part specifiers

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delimited mailbox by periods. A part specifier is either a part number that name no
longer exists.

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RFC 3501 IMAPv4 March 2003

6.3.10. STATUS Command

Arguments: mailbox name
status data item names

Responses: untagged responses: STATUS

Result: OK - status completed
NO - status failure: no status for that name
BAD - command unknown or one arguments invalid

The STATUS command requests the status of the following: HEADER, HEADER.FIELDS,
HEADER.FIELDS.NOT, MIME, and TEXT. An empty section
specification refers to indicated mailbox.
It does not change the entire message, including currently selected mailbox, nor does it
affect the
header.

Every message has at least one part number. Non-[MIME-IMB]
messages, and non-multipart [MIME-IMB] messages with no
encapsulated message, only have a part 1.

Multipart state of any messages are assigned consecutive part numbers, as
they occur in the message. If a particular part is of type
message or multipart, its parts queried mailbox (in
particular, STATUS MUST be indicated by a period
followed by the part number within that nested multipart part.

A part of type MESSAGE/RFC822 also has nested part numbers,
referring NOT cause messages to parts of lose the MESSAGE part's body. \Recent
flag).

The HEADER, HEADER.FIELDS, HEADER.FIELDS.NOT, STATUS command provides an alternative to opening a second
IMAP4rev1 connection and TEXT part
specifiers can be the sole part specifier or can be prefixed by
one or more numeric part specifiers, provided that the numeric
part specifier refers to a part of type MESSAGE/RFC822. The
MIME part specifier MUST be prefixed by one or more numeric
part specifiers.

The HEADER, HEADER.FIELDS, and HEADER.FIELDS.NOT part
specifiers refer to the [RFC-2822] header of the message or of doing an encapsulated [MIME-IMT] MESSAGE/RFC822 message.
HEADER.FIELDS and HEADER.FIELDS.NOT are followed by a list of
field-name (as defined in [RFC-2822]) names, and return a
subset of the header. The subset returned by HEADER.FIELDS
contains only those header fields with EXAMINE command on a field-name mailbox to
query that
matches one of mailbox's status without deselecting the names current
mailbox in the list; similarly, first IMAP4rev1 connection.

Unlike the subset
returned by HEADER.FIELDS.NOT contains only LIST command, the header fields
with a non-matching field-name. The field-matching STATUS command is
case-insensitive but otherwise exact. Subsetting does not
exclude the [RFC-2822] delimiting blank line between the header
and the body; guaranteed to
be fast in its response. Under certain circumstances, it can be
quite slow. In some implementations, the blank line server is included in all header fetches,
except in obliged to
open the case of a message which has no body and no blank
line.

The MIME part specifier refers mailbox read-only internally to obtain certain status
information. Also unlike the [MIME-IMB] header for
this part. LIST command, the STATUS command
does not accept wildcards.

Note: The TEXT part specifier refers STATUS command is intended to access the text body
status of mailboxes other than the message,
omitting currently selected
mailbox. Because the [RFC-2822] header.

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Here is an example of a complex message with some of its
part specifiers:

HEADER ([RFC-2822] header of STATUS command can cause the message)
TEXT ([RFC-2822] text body of
mailbox to be opened internally, and because this
information is available by other means on the message) MULTIPART/MIXED
1 TEXT/PLAIN
2 APPLICATION/OCTET-STREAM
3 MESSAGE/RFC822
3.HEADER ([RFC-2822] header of selected
mailbox, the message)
3.TEXT ([RFC-2822] text body of STATUS command SHOULD NOT be used on the message) MULTIPART/MIXED
3.1 TEXT/PLAIN
3.2 APPLICATION/OCTET-STREAM
4 MULTIPART/MIXED
4.1 IMAGE/GIF
4.1.MIME ([MIME-IMB] header
currently selected mailbox.

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The STATUS command MUST NOT be used as a "check for new
messages in the IMAGE/GIF)
4.2 MESSAGE/RFC822
4.2.HEADER ([RFC-2822] header of selected mailbox" operation (refer to
sections 7, 7.3.1, and 7.3.2 for more information about
the message)
4.2.TEXT ([RFC-2822] text body of proper method for new message checking).

Because the message) MULTIPART/MIXED
4.2.1 TEXT/PLAIN
4.2.2 MULTIPART/ALTERNATIVE
4.2.2.1 TEXT/PLAIN
4.2.2.2 TEXT/RICHTEXT

It STATUS command is possible not guaranteed to fetch a substring be fast
in its results, clients SHOULD NOT expect to be able to
issue many consecutive STATUS commands and obtain
reasonable performance.

The currently defined status data items that can be requested are:

MESSAGES
The number of messages in the designated text.
This is done by appending an open angle bracket ("<"), mailbox.

RECENT
The number of messages with the
octet position \Recent flag set.

UIDNEXT
The next unique identifier value of the first desired octet, a period, mailbox. Refer to
section 2.3.1.1 for more information.

UIDVALIDITY
The unique identifier validity value of the
maximum mailbox. Refer to
section 2.3.1.1 for more information.

UNSEEN
The number of octets desired, and a close angle bracket
(">") to messages which do not have the part specifier. If \Seen flag set.

Example: C: A042 STATUS blurdybloop (UIDNEXT MESSAGES)
S: * STATUS blurdybloop (MESSAGES 231 UIDNEXT 44292)
S: A042 OK STATUS completed

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6.3.11. APPEND Command

Arguments: mailbox name
OPTIONAL flag parenthesized list
OPTIONAL date/time string
message literal

Responses: no specific responses for this command

Result: OK - append completed
NO - append error: can't append to that mailbox, error
in flags or date/time or message text
BAD - command unknown or arguments invalid

The APPEND command appends the starting octet is beyond literal argument as a new message
to the end of the text, an empty string is returned.

Any partial fetch that attempts to read beyond specified destination mailbox. This argument
SHOULD be in the end format of an [RFC-2822] message. 8-bit
characters are permitted in the
text is truncated as appropriate. message. A partial fetch server implementation
that starts
at octet 0 is returned as unable to preserve 8-bit data properly MUST be able to
reversibly convert 8-bit APPEND data to 7-bit using a partial fetch, even if this
truncation happened. [MIME-IMB]
content transfer encoding.

Note: This means that BODY[]<0.2048> of a 1500-octet There MAY be exceptions, e.g., draft messages, in
which required [RFC-2822] header lines are omitted in
the message
will return BODY[]<0> with a literal argument to APPEND. The full
implications of size 1500, not
BODY[].

Note: A substring fetch of doing so MUST be understood and
carefully weighed.

If a HEADER.FIELDS or
HEADER.FIELDS.NOT part specifier is calculated after
subsetting the header.

The \Seen flag parenthesized list is implicitly set; if this causes specified, the flags to
change they SHOULD be included as part of the FETCH responses.

BODY.PEEK[<section>]<<partial>>

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An alternate form of BODY[<section>] that does not implicitly set
in the \Seen flag.

BODYSTRUCTURE
The [MIME-IMB] body structure resulting message; otherwise, the flag list of the message. This
resulting message is computed set to empty by default. In either case, the server by parsing
Recent flag is also set.

If a date-time is specified, the [MIME-IMB] header fields internal date SHOULD be set in
the
[RFC-2822] header and [MIME-IMB] headers.

ENVELOPE
The envelope structure resulting message; otherwise, the internal date of the message. This
resulting message is computed by set to the
server current date and time by parsing the [RFC-2822] header into default.

If the component
parts, defaulting various fields as necessary.

FLAGS
The flags that are set append is unsuccessful for this message.

INTERNALDATE
The internal date of any reason, the message.

RFC822
Functionally equivalent mailbox MUST be
restored to BODY[], differing in its state before the syntax of APPEND attempt; no partial
appending is permitted.

If the resulting untagged FETCH data (RFC822 destination mailbox does not exist, a server MUST return an
error, and MUST NOT automatically create the mailbox. Unless it
is returned).

RFC822.HEADER
Functionally equivalent to BODY.PEEK[HEADER], differing in certain that the
syntax destination mailbox can not be created, the
server MUST send the response code "[TRYCREATE]" as the prefix of
the resulting untagged FETCH data (RFC822.HEADER is
returned).

RFC822.SIZE
The [RFC-2822] size text of the message.

RFC822.TEXT
Functionally equivalent tagged NO response. This gives a hint to BODY[TEXT], differing in the syntax
of
client that it can attempt a CREATE command and retry the resulting untagged FETCH data (RFC822.TEXT is returned).

UID
The unique identifier for APPEND
if the message.

Example: C: A654 FETCH 2:4 (FLAGS BODY[HEADER.FIELDS (DATE FROM)])
S: * 2 FETCH ....
S: * 3 FETCH ....
S: * 4 FETCH ....
S: A654 OK FETCH completed CREATE is successful.

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RFC 3501 IMAPv4 March 2003

6.4.6. STORE Command

Arguments: sequence set
message data item name
value for message data item

Responses: untagged responses: FETCH

Result: OK - store completed
NO - store error: can't store that data
BAD - command unknown or arguments invalid

The STORE command alters data associated with a message in the
mailbox. Normally, STORE will return the updated value of the
data with an untagged FETCH response. A suffix of ".SILENT" in

If the data item name prevents mailbox is currently selected, the untagged FETCH, and normal new message
actions SHOULD occur. Specifically, the server SHOULD assume that notify the
client has determined immediately via an untagged EXISTS response. If the updated value
itself or server
does not care about the updated value.

Note: Regardless of whether or not the ".SILENT" suffix
was used, do so, the server SHOULD send an untagged FETCH
response if a change to client MAY issue a message's flags from an
external source is observed. The intent is that the
status of the flags is determinate without NOOP command (or failing
that, a race
condition.

The currently defined data items that can be stored are:

FLAGS <flag list>
Replace the flags CHECK command) after one or more APPEND commands.

Example: C: A003 APPEND saved-messages (\Seen) {310}
S: + Ready for the message (other than \Recent) with the
argument. The new value of the flags literal data
C: Date: Mon, 7 Feb 1994 21:52:25 -0800 (PST)
C: From: Fred Foobar <foobar@Blurdybloop.COM>
C: Subject: afternoon meeting
C: To: mooch@owatagu.siam.edu
C: Message-Id: <B27397-0100000@Blurdybloop.COM>
C: MIME-Version: 1.0
C: Content-Type: TEXT/PLAIN; CHARSET=US-ASCII
C:
C: Hello Joe, do you think we can meet at 3:30 tomorrow?
C:
S: A003 OK APPEND completed

Note: The APPEND command is returned as if not used for message delivery,
because it does not provide a FETCH
of those flags was done.

FLAGS.SILENT <flag list>
Equivalent mechanism to FLAGS, but without returning a new value.

+FLAGS <flag list>
Add transfer [SMTP]
envelope information.

6.4. Client Commands - Selected State

In the argument selected state, commands that manipulate messages in a mailbox
are permitted.

In addition to the flags for universal commands (CAPABILITY, NOOP, and LOGOUT),
and the message. The new value
of authenticated state commands (SELECT, EXAMINE, CREATE,
DELETE, RENAME, SUBSCRIBE, UNSUBSCRIBE, LIST, LSUB, STATUS, and
APPEND), the flags is returned as if following commands are valid in the selected state:
CHECK, CLOSE, EXPUNGE, SEARCH, FETCH, STORE, COPY, and UID.

6.4.1. CHECK Command

Arguments: none

Responses: no specific responses for this command

Result: OK - check completed
BAD - command unknown or arguments invalid

The CHECK command requests a FETCH checkpoint of those flags was done.

+FLAGS.SILENT <flag list>
Equivalent to +FLAGS, but without returning a new value.

-FLAGS <flag list>
Remove the argument from currently selected
mailbox. A checkpoint refers to any implementation-dependent
housekeeping associated with the flags for mailbox (e.g., resolving the message. The new
value
server's in-memory state of the flags is returned as if a FETCH of those flags was mailbox with the state on its

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done.

-FLAGS.SILENT <flag list>
Equivalent

disk) that is not normally executed as part of each command. A
checkpoint MAY take a non-instantaneous amount of real time to -FLAGS, but without returning
complete. If a server implementation has no such housekeeping
considerations, CHECK is equivalent to NOOP.

There is no guarantee that an EXISTS untagged response will happen
as a result of CHECK. NOOP, not CHECK, SHOULD be used for new value.
message polling.

Example: C: A003 STORE 2:4 +FLAGS (\Deleted)
S: * 2 FETCH (FLAGS (\Deleted \Seen))
S: * 3 FETCH (FLAGS (\Deleted))
S: * 4 FETCH (FLAGS (\Deleted \Flagged \Seen)) FXXZ CHECK
S: A003 FXXZ OK STORE completed

6.4.7. COPY CHECK Completed

6.4.2. CLOSE Command

Arguments: sequence set
mailbox name none

Responses: no specific responses for this command

Result: OK - copy completed
NO - copy error: can't copy those messages or to that
name close completed, now in authenticated state
BAD - command unknown or arguments invalid

The COPY CLOSE command copies the specified message(s) to the end of permanently removes all messages that have the
specified destination mailbox. The flags and internal date of
\Deleted flag set from the
message(s) SHOULD be preserved, currently selected mailbox, and returns
to the Recent flag SHOULD be set,
in authenticated state from the copy.

If selected state. No untagged
EXPUNGE responses are sent.

No messages are removed, and no error is given, if the destination mailbox does not exist, a server SHOULD return is
selected by an error. It SHOULD NOT automatically create the mailbox. Unless
it EXAMINE command or is certain that the destination otherwise selected read-only.

Even if a mailbox can not be created, the
server MUST send the response code "[TRYCREATE]" as the prefix of
the text of the tagged NO response. This gives a hint to the
client that it can attempt is selected, a CREATE SELECT, EXAMINE, or LOGOUT
command MAY be issued without previously issuing a CLOSE command.
The SELECT, EXAMINE, and retry the COPY if
the CREATE is successful.

If the COPY command is unsuccessful for any reason, server
implementations MUST restore LOGOUT commands implicitly close the destination
currently selected mailbox to its state
before without doing an expunge. However,
when many messages are deleted, a CLOSE-LOGOUT or CLOSE-SELECT
sequence is considerably faster than an EXPUNGE-LOGOUT or
EXPUNGE-SELECT because no untagged EXPUNGE responses (which the COPY attempt.
client would probably ignore) are sent.

Example: C: A003 COPY 2:4 MEETING A341 CLOSE
S: A003 A341 OK COPY CLOSE completed

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6.4.8. UID

6.4.3. EXPUNGE Command

Arguments: command name
command arguments none

Responses: untagged responses: FETCH, SEARCH EXPUNGE

Result: OK - UID command expunge completed
NO - UID command error expunge failure: can't expunge (e.g., permission
denied)
BAD - command unknown or arguments invalid

The UID command has two forms. In the first form, it takes as its
arguments a COPY, FETCH, or STORE EXPUNGE command with arguments
appropriate for permanently removes all messages that have the associated command. However,
\Deleted flag set from the numbers in currently selected mailbox. Before
returning an OK to the sequence set argument are unique identifiers instead of
message sequence numbers. Sequence set ranges are permitted,
however, there is no guarantee that unique identifiers be
contiguous.

A non-existent unique identifier client, an untagged EXPUNGE response is ignored without any error
sent for each message generated. Thus it that is possible for a UID FETCH command to
return OK without any data or a UID COPY or UID STORE to return removed.

Example: C: A202 EXPUNGE
S: * 3 EXPUNGE
S: * 3 EXPUNGE
S: * 5 EXPUNGE
S: * 8 EXPUNGE
S: A202 OK
without performing any operations. EXPUNGE completed

Note: In this example, messages 3, 4, 7, and 11 had the second form,
\Deleted flag set. See the UID command takes a description of the EXPUNGE
response for further explanation.

6.4.4. SEARCH command with Command

Arguments: OPTIONAL [CHARSET] specification
searching criteria (one or more)

Responses: REQUIRED untagged response: SEARCH

Result: OK - search completed
NO - search error: can't search that [CHARSET] or
criteria
BAD - command arguments. The interpretation of the unknown or arguments is invalid

The SEARCH command searches the same as with SEARCH; however, mailbox for messages that match
the numbers returned in a given searching criteria. Searching criteria consist of one
or more search keys. The untagged SEARCH response for from the server
contains a UID SEARCH command are unique identifiers instead listing of message sequence numbers. For example, the command UID SEARCH
1:100 UID 443:557 returns the unique identifiers numbers corresponding to
those messages that match the searching criteria.

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When multiple keys are specified, the result is the intersection
(AND function) of two sequence sets; all the message sequence number
range 1:100 and messages that match those keys. For
example, the UID range 443:557.

Note: criteria DELETED FROM "SMITH" SINCE 1-Feb-1994 refers
to all deleted messages from Smith that were placed in the above example, the UID range 443:557
appears. The same comment about mailbox
since February 1, 1994. A search key can also be a non-existent unique
identifier being ignored without any error message also
applies here. Hence, even if neither UID 443 parenthesized
list of one or 557
exist, this range is valid more search keys (e.g., for use with the OR and would include an existing
UID 495.

Also note that a UID range NOT
keys).

Server implementations MAY exclude [MIME-IMB] body parts with
terminal content media types other than TEXT and MESSAGE from
consideration in SEARCH matching.

The OPTIONAL [CHARSET] specification consists of 559:* always includes the
UID word
"CHARSET" followed by a registered [CHARSET]. It indicates the
[CHARSET] of the last message strings that appear in the mailbox, even if 559 is
higher search criteria.
[MIME-IMB] content transfer encodings, and [MIME-HDRS] strings in
[RFC-2822]/[MIME-IMB] headers, MUST be decoded before comparing
text in a [CHARSET] other than any assigned UID value. US-ASCII. US-ASCII MUST be
supported; other [CHARSET]s MAY be supported.

If the server does not support the specified [CHARSET], it MUST
return a tagged NO response (not a BAD). This is because response SHOULD
contain the
contents of BADCHARSET response code, which MAY list the
[CHARSET]s supported by the server.

In all search keys that use strings, a range are independent of message matches the order key if
the string is a substring of the
range endpoints. Thus, any UID range with * field. The matching is
case-insensitive.

The defined search keys are as one follows. Refer to the Formal
Syntax section for the precise syntactic definitions of the endpoints indicates at least one
arguments.

<sequence set>
Messages with message (the sequence numbers corresponding to the
specified message with sequence number set.

ALL
All messages in the highest numbered UID), unless mailbox; the
mailbox is empty. default initial key for
ANDing.

ANSWERED
Messages with the \Answered flag set.

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The number after

BCC <string>
Messages that contain the "*" specified string in an untagged FETCH response the envelope
structure's BCC field.

BEFORE <date>
Messages whose internal date (disregarding time and timezone)
is always a
message sequence number, not a unique identifier, even for earlier than the specified date.

BODY <string>
Messages that contain the specified string in the body of the
message.

CC <string>
Messages that contain the specified string in the envelope
structure's CC field.

DELETED
Messages with the \Deleted flag set.

DRAFT
Messages with the \Draft flag set.

FLAGGED
Messages with the \Flagged flag set.

FROM <string>
Messages that contain the specified string in the envelope
structure's FROM field.

HEADER <field-name> <string>
Messages that have a UID
command response. However, server implementations MUST implicitly
include header with the UID message data item as part specified field-name (as
defined in [RFC-2822]) and that contains the specified string
in the text of any FETCH response
caused by the header (what comes after the colon). If the
string to search is zero-length, this matches all messages that
have a UID command, header line with the specified field-name regardless of whether a UID was
the contents.

KEYWORD <flag>
Messages with the specified
as a message data item to keyword flag set.

LARGER <n>
Messages with an [RFC-2822] size larger than the FETCH.

Example: C: A999 UID FETCH 4827313:4828442 FLAGS
S: * 23 FETCH (FLAGS (\Seen) UID 4827313)
S: * 24 FETCH (FLAGS (\Seen) UID 4827943)
S: * 25 FETCH (FLAGS (\Seen) UID 4828442)
S: A999 OK UID FETCH completed

6.5. Client Commands - Experimental/Expansion

6.5.1. X<atom> Command

Arguments: implementation defined

Responses: implementation defined

Result: OK - command completed
NO - failure
BAD - command unknown or arguments invalid

Any command prefixed with an X is an experimental command.
Commands which are not part of this specification, a standard or
standards-track revision specified
number of this specification, or an
IESG-approved experimental protocol, MUST use the X prefix.

Any added untagged responses issued by an experimental command
MUST also be prefixed with an X. Server implementations MUST NOT
send any such untagged responses, unless octets.

NEW
Messages that have the client requested it
by issuing \Recent flag set but not the associated experimental command.

Example: C: a441 CAPABILITY
S: * CAPABILITY IMAP4rev1 XPIG-LATIN
S: a441 OK CAPABILITY completed
C: A442 XPIG-LATIN
S: * XPIG-LATIN ow-nay eaking-spay ig-pay atin-lay
S: A442 OK XPIG-LATIN ompleted-cay \Seen flag.
This is functionally equivalent to "(RECENT UNSEEN)".

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7. Server Responses

Server responses are in three forms: status responses, server data,
and command continuation request. The information contained in a
server response, identified by "Contents:" in

NOT <search-key>
Messages that do not match the response
descriptions below, is described by function, specified search key.

OLD
Messages that do not by syntax. The
precise syntax of server responses is described in have the Formal Syntax
section.

The client MUST be prepared \Recent flag set. This is
functionally equivalent to accept any response at all times.

Status responses can be tagged or untagged. Tagged status responses
indicate the completion result (OK, NO, or BAD status) of a client
command, and have a tag matching the command.

Some status responses, "NOT RECENT" (as opposed to "NOT
NEW").

ON <date>
Messages whose internal date (disregarding time and all server data, are untagged. An
untagged response timezone)
is indicated by within the token "*" instead of a tag.
Untagged status responses indicate server greeting, or server status specified date.

OR <search-key1> <search-key2>
Messages that does not indicate match either search key.

RECENT
Messages that have the completion of a command (for example, an
impending system shutdown alert). For historical reasons, untagged
server data responses are also called "unsolicited data", although
strictly speaking only unilateral server data is truly "unsolicited".

Certain server data MUST be recorded by \Recent flag set.

SEEN
Messages that have the client when it is
received; this \Seen flag set.

SENTBEFORE <date>
Messages whose [RFC-2822] Date: header (disregarding time and
timezone) is noted in the description of that data. Such data
conveys critical information which affects earlier than the interpretation of all
subsequent commands specified date.

SENTON <date>
Messages whose [RFC-2822] Date: header (disregarding time and responses (e.g. updates reflecting
timezone) is within the
creation specified date.

SENTSINCE <date>
Messages whose [RFC-2822] Date: header (disregarding time and
timezone) is within or destruction of messages).

Other server data SHOULD be recorded for later reference; if the
client does not need to record than the data, specified date.

SINCE <date>
Messages whose internal date (disregarding time and timezone)
is within or if recording later than the data has
no obvious purpose (e.g. a SEARCH response when no SEARCH command is
in progress), specified date.

SMALLER <n>
Messages with an [RFC-2822] size smaller than the data SHOULD be ignored.

An example specified
number of unilateral untagged server data occurs when octets.

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SUBJECT <string>
Messages that contain the IMAP
connection is specified string in selected state. In selected state, the server
checks envelope
structure's SUBJECT field.

TEXT <string>
Messages that contain the mailbox for new messages as part of command execution.
Normally, this is part of specified string in the execution header or
body of every command; hence, a
NOOP command suffices the message.

TO <string>
Messages that contain the specified string in the envelope
structure's TO field.

UID <sequence set>
Messages with unique identifiers corresponding to check for new messages. If new messages are
found, the server sends untagged EXISTS and RECENT responses
reflecting specified
unique identifier set. Sequence set ranges are permitted.

UNANSWERED
Messages that do not have the new size of \Answered flag set.

UNDELETED
Messages that do not have the mailbox. Server implementations \Deleted flag set.

UNDRAFT
Messages that
offer multiple simultaneous access to do not have the same mailbox SHOULD also
send appropriate unilateral untagged FETCH and EXPUNGE responses if
another agent changes \Draft flag set.

UNFLAGGED
Messages that do not have the state of any message flags or expunges any
messages.

Command continuation request responses use \Flagged flag set.

UNKEYWORD <flag>
Messages that do not have the token "+" instead of a
tag. These responses are sent by specified keyword flag set.

UNSEEN
Messages that do not have the server to indicate acceptance \Seen flag set.

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of an incomplete client command and readiness

Example: C: A282 SEARCH FLAGGED SINCE 1-Feb-1994 NOT FROM "Smith"
S: * SEARCH 2 84 882
S: A282 OK SEARCH completed
C: A283 SEARCH TEXT "string not in mailbox"
S: * SEARCH
S: A283 OK SEARCH completed
C: A284 SEARCH CHARSET UTF-8 TEXT {6}
C: XXXXXX
S: * SEARCH 43
S: A284 OK SEARCH completed

Note: Since this document is restricted to 7-bit ASCII
text, it is not possible to show actual UTF-8 data. The
"XXXXXX" is a placeholder for the remainder what would be 6 octets of
the command.

7.1. Server Responses
8-bit data in an actual transaction.

6.4.5. FETCH Command

Arguments: sequence set
message data item names or macro

Responses: untagged responses: FETCH

Result: OK - Status Responses

Status responses are OK, NO, BAD, PREAUTH and BYE. OK, NO, and fetch completed
NO - fetch error: can't fetch that data
BAD - command unknown or arguments invalid

The FETCH command retrieves data associated with a message in the
mailbox. The data items to be fetched can be tagged either a single atom
or untagged. PREAUTH and BYE are always untagged.

Status responses MAY include an OPTIONAL "response code". A response
code consists of a parenthesized list.

Most data inside square brackets items, identified in the form of an atom,
possibly followed by a space formal syntax under the
msg-att-static rule, are static and arguments. The response code
contains additional information or status codes MUST NOT change for client software
beyond any
particular message. Other data items, identified in the OK/NO/BAD condition, and are defined when there is formal
syntax under the msg-att-dynamic rule, MAY change, either as a
specific action that
result of a STORE command or due to external events.

For example, if a client receives an ENVELOPE for a
message when it already knows the envelope, it can take based upon
safely ignore the additional
information. newly transmitted envelope.

There are three macros which specify commonly-used sets of data
items, and can be used instead of data items. A macro must be
used by itself, and not in conjunction with other macros or data
items.

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ALL
Macro equivalent to: (FLAGS INTERNALDATE RFC822.SIZE ENVELOPE)

FAST
Macro equivalent to: (FLAGS INTERNALDATE RFC822.SIZE)

FULL
Macro equivalent to: (FLAGS INTERNALDATE RFC822.SIZE ENVELOPE
BODY)

The currently defined response codes data items that can be fetched are:

ALERT

BODY
Non-extensible form of BODYSTRUCTURE.

BODY[<section>]<<partial>>
The human-readable text contains a special alert that MUST be
presented to the user in of a fashion that calls the user's
attention to the message.

BADCHARSET

Optionally followed by particular body section. The section
specification is a parenthesized list set of charsets. A
SEARCH failed because the given charset is not supported zero or more part specifiers
delimited by
this implementation. If the optional list of charsets periods. A part specifier is
given, this lists the charsets that are supported by this
implementation.

CAPABILITY

Followed by either a list part number
or one of capabilities. This can appear in the
initial OK or PREAUTH response to transmit an initial
capabilities list. This makes it unnecessary for a client following: HEADER, HEADER.FIELDS,
HEADER.FIELDS.NOT, MIME, and TEXT. An empty section
specification refers to
send a separate CAPABILITY command if it recognizes this
response.

PARSE

The human-readable text represents an error in parsing the
[RFC-2822] header or entire message, including the
header.

Every message has at least one part number. Non-[MIME-IMB]
messages, and non-multipart [MIME-IMB] headers of messages with no
encapsulated message, only have a message part 1.

Multipart messages are assigned consecutive part numbers, as
they occur in the

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mailbox.

PERMANENTFLAGS

Followed by message. If a parenthesized list of flags, indicates which particular part is of type
message or multipart, its parts MUST be indicated by a period
followed by the known flags part number within that nested multipart part.

A part of type MESSAGE/RFC822 also has nested part numbers,
referring to parts of the client MESSAGE part's body.

The HEADER, HEADER.FIELDS, HEADER.FIELDS.NOT, and TEXT part
specifiers can change permanently. Any
flags that are in the FLAGS untagged response, but not be the
PERMANENTFLAGS list, sole part specifier or can not be set permanently. If prefixed by
one or more numeric part specifiers, provided that the client
attempts numeric
part specifier refers to STORE a flag that is not in the PERMANENTFLAGS
list, the server will either ignore the change or store the
state change for the remainder part of the current session only. type MESSAGE/RFC822. The PERMANENTFLAGS list can also include the special flag \*,
which indicates that it is possible to create new keywords
MIME part specifier MUST be prefixed by
attempting one or more numeric
part specifiers.

The HEADER, HEADER.FIELDS, and HEADER.FIELDS.NOT part
specifiers refer to store those flags in the mailbox.

READ-ONLY

The mailbox is selected read-only, [RFC-2822] header of the message or its access while selected
has changed from read-write to read-only.

READ-WRITE

The mailbox is selected read-write, or its access while
selected has changed from read-only to read-write.

TRYCREATE

An APPEND or COPY attempt is failing because the target mailbox
does not exist of
an encapsulated [MIME-IMT] MESSAGE/RFC822 message.
HEADER.FIELDS and HEADER.FIELDS.NOT are followed by a list of
field-name (as opposed to some other reason). This is defined in [RFC-2822]) names, and return a
hint to

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subset of the client header. The subset returned by HEADER.FIELDS
contains only those header fields with a field-name that
matches one of the operation can succeed if names in the
mailbox is first created by list; similarly, the CREATE command.

UIDNEXT

Followed subset
returned by a decimal number, indicates HEADER.FIELDS.NOT contains only the next unique
identifier value. Refer to section 2.3.1.1 for more
information.

UIDVALIDITY

Followed by header fields
with a decimal number, indicates non-matching field-name. The field-matching is
case-insensitive but otherwise exact. Subsetting does not
exclude the unique identifier
validity value. Refer [RFC-2822] delimiting blank line between the header
and the body; the blank line is included in all header fetches,
except in the case of a message which has no body and no blank
line.

The MIME part specifier refers to section 2.3.1.1 the [MIME-IMB] header for more information.

UNSEEN

Followed by a decimal number, indicates
this part.

The TEXT part specifier refers to the number text body of the first message,
omitting the [RFC-2822] header.

Here is an example of a complex message without with some of its
part specifiers:

HEADER ([RFC-2822] header of the \Seen flag set.

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TEXT ([RFC-2822] text body of the message) MULTIPART/MIXED
1 April 2003

Additional response codes defined by particular client or server
implementations SHOULD be prefixed with an "X" until they are
added to a revision TEXT/PLAIN
2 APPLICATION/OCTET-STREAM
3 MESSAGE/RFC822
3.HEADER ([RFC-2822] header of this protocol. Client implementations
SHOULD ignore response codes that they do not recognize.

7.1.1. OK Response

Contents: OPTIONAL response code
human-readable the message)
3.TEXT ([RFC-2822] text

The OK response indicates an information message from body of the server.
When tagged, it indicates successful completion message) MULTIPART/MIXED
3.1 TEXT/PLAIN
3.2 APPLICATION/OCTET-STREAM
4 MULTIPART/MIXED
4.1 IMAGE/GIF
4.1.MIME ([MIME-IMB] header for the IMAGE/GIF)
4.2 MESSAGE/RFC822
4.2.HEADER ([RFC-2822] header of the associated
command. The human-readable message)
4.2.TEXT ([RFC-2822] text MAY be presented body of the message) MULTIPART/MIXED
4.2.1 TEXT/PLAIN
4.2.2 MULTIPART/ALTERNATIVE
4.2.2.1 TEXT/PLAIN
4.2.2.2 TEXT/RICHTEXT

It is possible to fetch a substring of the user as
an information message. The untagged form indicates designated text.
This is done by appending an
information-only message; open angle bracket ("<"), the nature
octet position of the information MAY be
indicated by first desired octet, a response code.

The untagged form period, the
maximum number of octets desired, and a close angle bracket
(">") to the part specifier. If the starting octet is also used as one beyond
the end of three possible greetings
at connection startup. It indicates the text, an empty string is returned.

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Any partial fetch that attempts to read beyond the connection end of the
text is not
yet authenticated and truncated as appropriate. A partial fetch that a LOGIN command starts
at octet 0 is needed.

Example: S: * OK IMAP4rev1 server ready
C: A001 LOGIN fred blurdybloop
S: * OK [ALERT] System shutdown in 10 minutes
S: A001 OK LOGIN Completed

7.1.2. NO Response

Contents: OPTIONAL response code
human-readable text

The NO response indicates an operational error returned as a partial fetch, even if this
truncation happened.

Note: This means that BODY[]<0.2048> of a 1500-octet message from the
server. When tagged, it indicates unsuccessful completion
will return BODY[]<0> with a literal of size 1500, not
BODY[].

Note: A substring fetch of the
associated command. The untagged form indicates a warning; HEADER.FIELDS or
HEADER.FIELDS.NOT part specifier is calculated after
subsetting the
command can still complete successfully. header.

The human-readable text
describes the condition.

Example: C: A222 COPY 1:2 owatagusiam
S: * NO Disk is 98% full, please delete unnecessary data
S: A222 OK COPY completed
C: A223 COPY 3:200 blurdybloop
S: * NO Disk is 98% full, please delete unnecessary data
S: * NO Disk is 99% full, please delete unnecessary data
S: A223 NO COPY failed: disk \Seen flag is full

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7.1.3. BAD Response

Contents: OPTIONAL response code
human-readable text

The BAD response indicates an error message from the server. When
tagged, it reports a protocol-level error in the client's command; implicitly set; if this causes the tag indicates flags to
change, they SHOULD be included as part of the command FETCH responses.

BODY.PEEK[<section>]<<partial>>
An alternate form of BODY[<section>] that caused does not implicitly
set the error. \Seen flag.

BODYSTRUCTURE
The untagged
form indicates a protocol-level error for which [MIME-IMB] body structure of the message. This is computed
by the associated
command can not be determined; it can also indicate an internal server failure. The human-readable text describes by parsing the condition.

Example: C: ...very long command line...
S: * BAD Command line too long
C: ...empty line...
S: * BAD Empty command line
C: A443 EXPUNGE
S: * BAD Disk crash, attempting salvage to a new disk!
S: * OK Salvage successful, no data lost
S: A443 OK Expunge completed

7.1.4. PREAUTH Response

Contents: OPTIONAL response code
human-readable text

The PREAUTH response is always untagged, [MIME-IMB] header fields in the
[RFC-2822] header and is one [MIME-IMB] headers.

ENVELOPE
The envelope structure of three
possible greetings at connection startup. It indicates that the
connection has already been authenticated by external means and
thus no LOGIN command message. This is needed.

Example: S: * PREAUTH IMAP4rev1 computed by the
server logged in by parsing the [RFC-2822] header into the component
parts, defaulting various fields as Smith

7.1.5. BYE Response

Contents: OPTIONAL response code
human-readable text necessary.

FLAGS
The BYE response is always untagged, and indicates flags that are set for this message.

INTERNALDATE
The internal date of the server
is about message.

RFC822
Functionally equivalent to close BODY[], differing in the connection. The human-readable text MAY be
displayed to syntax of
the user resulting untagged FETCH data (RFC822 is returned).

RFC822.HEADER
Functionally equivalent to BODY.PEEK[HEADER], differing in a status report by the client. The BYE
response is sent under one of four conditions:

1) as part
syntax of a normal logout sequence. The server will close the connection after sending resulting untagged FETCH data (RFC822.HEADER is
returned).

RFC822.SIZE
The [RFC-2822] size of the tagged OK response to the
LOGOUT command. message.

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2) as a panic shutdown announcement. The server closes the
connection immediately.

3) as an announcement of an inactivity autologout. The server
closes

RFC822.TEXT
Functionally equivalent to BODY[TEXT], differing in the connection immediately.

4) as one syntax
of three possible greetings at connection startup,
indicating that the server resulting untagged FETCH data (RFC822.TEXT is not willing to accept a
connection from this client. returned).

UID
The server closes unique identifier for the
connection immediately.

The difference between a BYE that occurs as part of a normal
LOGOUT message.

Example: C: A654 FETCH 2:4 (FLAGS BODY[HEADER.FIELDS (DATE FROM)])
S: * 2 FETCH ....
S: * 3 FETCH ....
S: * 4 FETCH ....
S: A654 OK FETCH completed

6.4.6. STORE Command

Arguments: sequence (the first case) and a BYE set
message data item name
value for message data item

Responses: untagged responses: FETCH

Result: OK - store completed
NO - store error: can't store that occurs because of data
BAD - command unknown or arguments invalid

The STORE command alters data associated with a failure (the other three cases) is that the connection closes
immediately message in the failure case. In all cases
mailbox. Normally, STORE will return the updated value of the client SHOULD
continue to read response
data from with an untagged FETCH response. A suffix of ".SILENT" in
the server until data item name prevents the
connection is closed; this will ensure that any pending untagged
or completion responses are read FETCH, and processed.

Example: S: * BYE Autologout; idle for too long

7.2. Server Responses - Server and Mailbox Status

These responses are always untagged. This is how server and mailbox
status data are transmitted from the server to
SHOULD assume that the client. Many client has determined the updated value
itself or does not care about the updated value.

Note: Regardless of
these responses typically result from a command with whether or not the same name.

7.2.1. CAPABILITY Response

Contents: capability listing

The CAPABILITY ".SILENT" suffix
was used, the server SHOULD send an untagged FETCH
response occurs as if a result of change to a CAPABILITY
command. message's flags from an
external source is observed. The capability listing contains a space-separated
listing of capability names intent is that the server supports. The
capability listing MUST include the atom "IMAP4rev1".

In addition, client and server implementations MUST implement
status of the
STARTTLS, LOGINDISABLED, and AUTH=PLAIN (described in [IMAP-TLS])
capabilities. See flags is determinate without a race
condition.

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The currently defined data items that can be stored are:

FLAGS <flag list>
Replace the Security Considerations section flags for
important information.

A capability name which begins the message (other than \Recent) with "AUTH=" indicates that the
server supports that particular authentication mechanism.
argument. The LOGINDISABLED capability indicates that new value of the LOGIN command flags is
disabled, and that the server will respond with returned as if a tagged NO
response to any attempt FETCH
of those flags was done.

FLAGS.SILENT <flag list>
Equivalent to use FLAGS, but without returning a new value.

+FLAGS <flag list>
Add the LOGIN command even if argument to the user
name and password are valid. An IMAP client MUST NOT issue flags for the

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Other capability names indicate that the server supports an
extension, revision, or amendment to message. The new value
of the IMAP4rev1 protocol.
Server responses MUST conform flags is returned as if a FETCH of those flags was done.

+FLAGS.SILENT <flag list>
Equivalent to this document until the client
issues +FLAGS, but without returning a command that uses the associated capability.

Capability names MUST either begin with "X" or be standard or
standards-track IMAP4rev1 extensions, revisions, or amendments
registered with IANA. A server MUST NOT offer unregistered or
non-standard capability names, unless such names are prefixed with
an "X".

Client implementations SHOULD NOT require any capability name
other than "IMAP4rev1", and MUST ignore any unknown capability
names.

A server MAY send capabilities automatically, by using new value.

-FLAGS <flag list>
Remove the
CAPABILITY response code in argument from the initial PREAUTH or OK responses,
and by sending an updated CAPABILITY response code in flags for the tagged
OK response as part message. The new
value of a successful authentication. It the flags is
unnecessary for returned as if a client FETCH of those flags was
done.

-FLAGS.SILENT <flag list>
Equivalent to send -FLAGS, but without returning a separate CAPABILITY command if
it recognizes these automatic capabilities. new value.

Example: C: A003 STORE 2:4 +FLAGS (\Deleted)
S: * CAPABILITY IMAP4rev1 STARTTLS AUTH=GSSAPI XPIG-LATIN

7.2.2. LIST Response

Contents: 2 FETCH (FLAGS (\Deleted \Seen))
S: * 3 FETCH (FLAGS (\Deleted))
S: * 4 FETCH (FLAGS (\Deleted \Flagged \Seen))
S: A003 OK STORE completed

6.4.7. COPY Command

Arguments: sequence set
mailbox name attributes
hierarchy delimiter
name

The LIST response occurs as a result of a LIST command. It
returns a single name that matches the LIST specification. There
can be multiple LIST

Responses: no specific responses for a single LIST command.

Four name attributes are defined:

\Noinferiors

It is not possible for any child levels of hierarchy to exist
under this name; no child levels exist now and none can be
created in the future.

\Noselect command

Result: OK - copy completed
NO - copy error: can't copy those messages or to that
name
BAD - command unknown or arguments invalid

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It is not possible

The COPY command copies the specified message(s) to use this name as a selectable the end of the
specified destination mailbox.

\Marked The mailbox has been marked "interesting" by flags and internal date of the server;
message(s) SHOULD be preserved, and the
mailbox probably contains messages that have been added since Recent flag SHOULD be set,
in the last time copy.

If the mailbox was selected.

\Unmarked

The destination mailbox does not contain any additional messages since the
last time exist, a server SHOULD return
an error. It SHOULD NOT automatically create the mailbox was selected.

If mailbox. Unless
it is certain that the destination mailbox can not feasible for be created, the
server MUST send the response code "[TRYCREATE]" as the prefix of
the text of the tagged NO response. This gives a hint to determine whether the
mailbox is "interesting" or not, or
client that it can attempt a CREATE command and retry the COPY if
the name CREATE is a \Noselect
name, successful.

If the server SHOULD NOT send either \Marked COPY command is unsuccessful for any reason, server
implementations MUST restore the destination mailbox to its state
before the COPY attempt.

Example: C: A003 COPY 2:4 MEETING
S: A003 OK COPY completed

6.4.8. UID Command

Arguments: command name
command arguments

Responses: untagged responses: FETCH, SEARCH

Result: OK - UID command completed
NO - UID command error
BAD - command unknown or \Unmarked. arguments invalid

The hierarchy delimiter is UID command has two forms. In the first form, it takes as its
arguments a character used to delimit levels of
hierarchy COPY, FETCH, or STORE command with arguments
appropriate for the associated command. However, the numbers in a mailbox name.
the sequence set argument are unique identifiers instead of
message sequence numbers. Sequence set ranges are permitted, but
there is no guarantee that unique identifiers will be contiguous.

A client can use non-existent unique identifier is ignored without any error
message generated. Thus, it is possible for a UID FETCH command
to create child
mailboxes, and to search higher return an OK without any data or lower levels of naming
hierarchy. All children of a top-level hierarchy node MUST use UID COPY or UID STORE to
return an OK without performing any operations.

In the same separator character. A NIL hierarchy delimiter means
that no hierarchy exists; second form, the name is UID command takes a "flat" name. SEARCH command with
SEARCH command arguments. The name represents an unambiguous left-to-right hierarchy, and
MUST be valid for use as a reference in LIST and LSUB commands.
Unless \Noselect interpretation of the arguments is indicated,
the name MUST also be valid same as an
argument for commands, such as SELECT, that accept mailbox names.

Example: S: * LIST (\Noselect) "/" ~/Mail/foo

7.2.3. LSUB Response

Contents: name attributes
hierarchy delimiter
name

The LSUB response occurs as a result of an LSUB command. It
returns a single name that matches with SEARCH; however, the LSUB specification. There
can be multiple LSUB responses numbers returned in a SEARCH
response for a single LSUB command. The
data is identical in format to the LIST response.

Example: S: * LSUB () "." #news.comp.mail.misc UID SEARCH command are unique identifiers instead

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7.2.4 STATUS Response

Contents: name
status parenthesized list

The STATUS response occurs as a result

of an STATUS command. It message sequence numbers. For example, the command UID SEARCH
1:100 UID 443:557 returns the mailbox name that matches unique identifiers corresponding to
the STATUS specification intersection of two sequence sets, the message sequence number
range 1:100 and the requested mailbox status information.

Example: S: * STATUS blurdybloop (MESSAGES 231 UIDNEXT 44292)

7.2.5. SEARCH Response

Contents: zero or more numbers UID range 443:557.

Note: in the above example, the UID range 443:557
appears. The SEARCH response occurs as a result of same comment about a SEARCH non-existent unique
identifier being ignored without any error message also
applies here. Hence, even if neither UID 443 or 557
exist, this range is valid and would include an existing
UID SEARCH
command. The number(s) refer to those messages 495.

Also note that match a UID range of 559:* always includes the
search criteria. For SEARCH, these are message sequence numbers;
for
UID SEARCH, these are unique identifiers. Each number is
delimited by a space.

Example: S: * SEARCH 2 3 6

7.2.6. FLAGS Response

Contents: flag parenthesized list

The FLAGS response occurs as a result of a SELECT or EXAMINE
command. The flag parenthesized list identifies the flags (at a
minimum, last message in the system-defined flags) that are applicable for this
mailbox. Flags other mailbox, even if 559 is
higher than any assigned UID value. This is because the system flags can also exist,
depending on server implementation.

The update from
contents of a range are independent of the FLAGS response MUST be recorded by order of the client.

Example: S:
range endpoints. Thus, any UID range with * FLAGS (\Answered \Flagged \Deleted \Seen \Draft)

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7.3. Server Responses - Mailbox Size

These responses are always untagged. This is how changes in the size as one of
the mailbox are transmitted from endpoints indicates at least one message (the
message with the server to highest numbered UID), unless the client.
Immediately following
mailbox is empty.

The number after the "*" token in an untagged FETCH response is a number that represents always a
message count.

7.3.1. EXISTS Response

Contents: none

The EXISTS response reports the number of messages in sequence number, not a unique identifier, even for a UID
command response. However, server implementations MUST implicitly
include the mailbox.
This response occurs UID message data item as a result part of any FETCH response
caused by a SELECT or EXAMINE UID command,
and if the size regardless of whether a UID was specified
as a message data item to the mailbox changes (e.g. new messages). FETCH.

Note: The update from rule about including the EXISTS response MUST be recorded by the
client.

Example: S: * 23 EXISTS

7.3.2. RECENT Response

Contents: none

The RECENT response reports the number of messages with the
\Recent flag set. This response occurs UID message data item as a result part
of a SELECT or
EXAMINE command, and if the size of the mailbox changes (e.g. new
messages).

Note: It is not guaranteed that FETCH response primarily applies to the message sequence
numbers of recent messages will be UID FETCH and UID
STORE commands, including a contiguous range of
the highest n messages in the mailbox (where n is the
value reported by the RECENT response). Examples of
situations in which this is UID FETCH command that does not the case are: multiple
clients having the same mailbox open (the first session
to be notified will see it as recent, others will
probably see it
include UID as non-recent), and when the mailbox is
re-ordered by a non-IMAP agent.

The only reliable way to identify recent messages is to
look at message flags to see which have data item. Although it is unlikely that
the \Recent flag
set, or other UID commands will cause an untagged FETCH, this rule
applies to do a SEARCH RECENT.

The update from the RECENT response MUST be recorded by the
client. these commands as well.

Example: C: A999 UID FETCH 4827313:4828442 FLAGS
S: * 5 RECENT 23 FETCH (FLAGS (\Seen) UID 4827313)
S: * 24 FETCH (FLAGS (\Seen) UID 4827943)
S: * 25 FETCH (FLAGS (\Seen) UID 4828442)
S: A999 OK UID FETCH completed

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7.4. Server Responses - Message Status

These responses are always untagged. This

6.5. Client Commands - Experimental/Expansion

6.5.1. X<atom> Command

Arguments: implementation defined

Responses: implementation defined

Result: OK - command completed
NO - failure
BAD - command unknown or arguments invalid

Any command prefixed with an X is how message data an experimental command.
Commands which are
transmitted from the server to the client, often as a result not part of this specification, a standard or
standards-track revision of this specification, or an
IESG-approved experimental protocol, MUST use the X prefix.

Any added untagged responses issued by an experimental command
MUST also be prefixed with an X. Server implementations MUST NOT
send any such untagged responses, unless the same name. Immediately following the "*" token is a
number that represents a message sequence number.

7.4.1. EXPUNGE Response

Contents: none

The EXPUNGE response reports that the specified message sequence
number has been permanently removed from client requested it
by issuing the mailbox. associated experimental command.

7. Server Responses

Server responses are in three forms: status responses, server data,
and command continuation request. The message
sequence number for each successive message information contained in a
server response, identified by "Contents:" in the mailbox response
descriptions below, is
immediately decremented described by 1, and this decrement is reflected in
message sequence numbers in subsequent responses (including other
untagged EXPUNGE responses). function, not by syntax. The EXPUNGE response also decrements the number
precise syntax of messages server responses is described in the
mailbox; it is not necessary Formal Syntax
section.

The client MUST be prepared to send an EXISTS accept any response with at all times.

Status responses can be tagged or untagged. Tagged status responses
indicate the
new value.

As a completion result (OK, NO, or BAD status) of the immediate decrement rule, message sequence
numbers that appear in a set of successive EXPUNGE responses
depend upon whether client
command, and have a tag matching the messages command.

Some status responses, and all server data, are removed starting from lower
numbers to higher numbers, or from higher numbers to lower
numbers. For example, if untagged. An
untagged response is indicated by the last 5 messages in a 9-message
mailbox are expunged; token "*" instead of a "lower to higher" server will send five
untagged EXPUNGE tag.
Untagged status responses for message sequence number 5, whereas indicate server greeting, or server status

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RFC 3501 IMAPv4 March 2003

that does not indicate the completion of a "higher to lower server" will send successive command (for example, an
impending system shutdown alert). For historical reasons, untagged EXPUNGE
server data responses for message sequence numbers 9, 8, 7, 6, and 5.

An EXPUNGE response are also called "unsolicited data", although
strictly speaking, only unilateral server data is truly
"unsolicited".

Certain server data MUST NOT be sent recorded by the client when no command it is in
progress; nor while responding to a FETCH, STORE, or SEARCH
command. This rule
received; this is necessary to prevent a loss noted in the description of
synchronization that data. Such data
conveys critical information which affects the interpretation of message sequence numbers between client all
subsequent commands and
server. A command is not "in progress" until the complete command
has been received; in particular, a command is not "in progress"
during responses (e.g., updates reflecting the negotiation
creation or destruction of command continuation.

Note: UID FETCH, UID STORE, and UID SEARCH are different
commands from FETCH, STORE, and SEARCH. An EXPUNGE
response MAY be sent during an UID command.

The update from the EXPUNGE response MUST messages).

Other server data SHOULD be recorded by for later reference; if the
client.

Example: S: * 44 EXPUNGE

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7.4.2. FETCH Response

Contents: message data

The FETCH response returns data about a message
client does not need to record the data, or if recording the client.
The data are pairs of data item names and their values in
parentheses. This has
no obvious purpose (e.g., a SEARCH response occurs as when no SEARCH command is
in progress), the result data SHOULD be ignored.

An example of a FETCH or
STORE command, as well as by unilateral untagged server decision (e.g. flag
updates).

The current data items are:

BODY
A form of BODYSTRUCTURE without extension data.

BODY[<section>]<<origin octet>>
A string expressing occurs when the body contents of IMAP
connection is in the specified section.
The string SHOULD be interpreted by selected state. In the client according to selected state, the
content transfer encoding, body type, and subtype.

If
server checks the origin octet is specified, mailbox for new messages as part of command
execution. Normally, this string is a substring part of the entire body contents, starting at that origin octet. This
means that BODY[]<0> MAY be truncated, but BODY[] is NEVER
truncated.

Note: The origin octet facility MUST NOT be used by execution of every command;
hence, a NOOP command suffices to check for new messages. If new
messages are found, the server
in a FETCH response unless sends untagged EXISTS and RECENT
responses reflecting the client specifically requested
it by means new size of a the mailbox. Server
implementations that offer multiple simultaneous access to the same
mailbox SHOULD also send appropriate unilateral untagged FETCH of a BODY[<section>]<<partial>> data
item.

8-bit textual data is permitted and
EXPUNGE responses if a [CHARSET] identifier is
part of another agent changes the body parameter parenthesized list for this section.
Note that headers (part specifiers HEADER or MIME, state of any message
flags or expunges any messages.

Command continuation request responses use the
header portion token "+" instead of a MESSAGE/RFC822 part), MUST be 7-bit; 8-bit
characters
tag. These responses are not permitted in headers. Note also that the
[RFC-2822] delimiting blank line between sent by the header server to indicate acceptance
of an incomplete client command and readiness for the
body is not affected by header line subsetting; remainder of
the blank line
is command.

7.1. Server Responses - Status Responses

Status responses are OK, NO, BAD, PREAUTH and BYE. OK, NO, and BAD
can be tagged or untagged. PREAUTH and BYE are always included as part untagged.

Status responses MAY include an OPTIONAL "response code". A response
code consists of header data, except data inside square brackets in the case form of an atom,
possibly followed by a message which has no body space and no blank line.

Non-textual data such as binary data MUST be transfer encoded
into a textual form such as BASE64 prior to being sent to the
client. To derive the original binary data, the arguments. The response code
contains additional information or status codes for client MUST
decode software
beyond the transfer encoded string.

BODYSTRUCTURE
A parenthesized list OK/NO/BAD condition, and are defined when there is a
specific action that describes the [MIME-IMB] body
structure of a message. This is computed by client can take based upon the server by additional
information.

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parsing the [MIME-IMB] header fields, defaulting various fields
as necessary.

For example, a simple

The currently defined response codes are:

ALERT

The human-readable text message of 48 lines and 2279 octets
can have contains a body structure of: ("TEXT" "PLAIN" ("CHARSET"
"US-ASCII") NIL NIL "7BIT" 2279 48)

Multiple parts are indicated by parenthesis nesting. Instead
of special alert that MUST be
presented to the user in a body type as fashion that calls the first element of user's
attention to the message.

BADCHARSET

Optionally followed by a parenthesized list
there is a sequence of one or more nested body structures. The
second element of charsets. A
SEARCH failed because the parenthesized given charset is not supported by
this implementation. If the optional list of charsets is
given, this lists the multipart
subtype (mixed, digest, parallel, alternative, etc.).

For example, charsets that are supported by this
implementation.

CAPABILITY

Followed by a two part message consisting list of capabilities. This can appear in the
initial OK or PREAUTH response to transmit an initial
capabilities list. This makes it unnecessary for a text and client to
send a
BASE64-encoded separate CAPABILITY command if it recognizes this
response.

PARSE

The human-readable text attachment can have a body structure of:
(("TEXT" "PLAIN" ("CHARSET" "US-ASCII") NIL NIL "7BIT" 1152
23)("TEXT" "PLAIN" ("CHARSET" "US-ASCII" "NAME" "cc.diff")
"<960723163407.20117h@cac.washington.edu>" "Compiler diff"
"BASE64" 4554 73) "MIXED")

Extension data follows the multipart subtype. Extension data
is never returned with the BODY fetch, but can be returned with
a BODYSTRUCTURE fetch. Extension data, if present, MUST be represents an error in parsing the defined order.

The extension data
[RFC-2822] header or [MIME-IMB] headers of a multipart body part are message in the
following order:

body parameter parenthesized list
A
mailbox.

PERMANENTFLAGS

Followed by a parenthesized list of attribute/value pairs [e.g. ("foo"
"bar" "baz" "rag") where "bar" is the value flags, indicates which of "foo" and
"rag" is
the value of "baz"] as defined known flags the client can change permanently. Any flags
that are in [MIME-IMB].

body disposition
A parenthesized the FLAGS untagged response, but not the
PERMANENTFLAGS list, consisting of a disposition type
string followed by can not be set permanently. If the client
attempts to STORE a parenthesized list of disposition
attribute/value pairs as defined flag that is not in [DISPOSITION].

body language
A string the PERMANENTFLAGS
list, the server will either ignore the change or parenthesized list giving store the body language
value as defined in [LANGUAGE-TAGS].

body location
A string list giving
state change for the body content URI as defined in
[LOCATION].

Any following extension data are not yet defined in this
version remainder of the protocol. Such extension data current session only.
The PERMANENTFLAGS list can consist of also include the special flag \*,
which indicates that it is possible to create new keywords by
attempting to store those flags in the mailbox.

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zero

READ-ONLY

The mailbox is selected read-only, or more NILs, strings, numbers, its access while selected
has changed from read-write to read-only.

READ-WRITE

The mailbox is selected read-write, or potentially nested
parenthesized lists of such data. Client implementations its access while
selected has changed from read-only to read-write.

TRYCREATE

An APPEND or COPY attempt is failing because the target mailbox
does not exist (as opposed to some other reason). This is a
hint to the client that
do the operation can succeed if the
mailbox is first created by the CREATE command.

UIDNEXT

Followed by a BODYSTRUCTURE fetch MUST be prepared decimal number, indicates the next unique
identifier value. Refer to accept such
extension data. Server implementations MUST NOT send such
extension data until it has been section 2.3.1.1 for more
information.

UIDVALIDITY

Followed by a decimal number, indicates the unique identifier
validity value. Refer to section 2.3.1.1 for more information.

UNSEEN

Followed by a decimal number, indicates the number of the first
message without the \Seen flag set.

Additional response codes defined by particular client or server
implementations SHOULD be prefixed with an "X" until they are
added to a revision of this protocol. Client implementations
SHOULD ignore response codes that they do not recognize.

7.1.1. OK Response

Contents: OPTIONAL response code
human-readable text

The basic fields OK response indicates an information message from the server.
When tagged, it indicates successful completion of a non-multipart body part are in the
following order:

body type
A string giving associated
command. The human-readable text MAY be presented to the content media type name user as defined in
[MIME-IMB].

body subtype
A string giving
an information message. The untagged form indicates an

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RFC 3501 IMAPv4 March 2003

information-only message; the content subtype name as defined in
[MIME-IMB].

body parameter parenthesized list
A parenthesized list nature of attribute/value pairs [e.g. ("foo"
"bar" "baz" "rag") where "bar" is the value of "foo" and
"rag" information MAY be
indicated by a response code.

The untagged form is the value of "baz"] as defined in [MIME-IMB].

body id
A string giving the content id as defined in [MIME-IMB].

body description
A string giving the content description as defined in
[MIME-IMB].

body encoding
A string giving the content transfer encoding also used as defined in
[MIME-IMB].

body size
A number giving the size one of the body in octets. Note three possible greetings
at connection startup. It indicates that
this size is the size in its transfer encoding and connection is not the
resulting size after any decoding.

A body type of type MESSAGE and subtype RFC822 contains,
immediately after the basic fields, the envelope structure,
body structure,
yet authenticated and size that a LOGIN command is needed.

Example: S: * OK IMAP4rev1 server ready
C: A001 LOGIN fred blurdybloop
S: * OK [ALERT] System shutdown in 10 minutes
S: A001 OK LOGIN Completed

7.1.2. NO Response

Contents: OPTIONAL response code
human-readable text lines of

The NO response indicates an operational error message from the encapsulated
message.

A body type
server. When tagged, it indicates unsuccessful completion of type TEXT contains, immediately after the basic
fields, the size of
associated command. The untagged form indicates a warning; the body in
command can still complete successfully. The human-readable text lines. Note that this
size is the size in its content transfer encoding and not
describes the
resulting size after any decoding.

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Extension condition.

Example: C: A222 COPY 1:2 owatagusiam
S: * NO Disk is 98% full, please delete unnecessary data follows the basic fields and the type-specific
fields listed above. Extension
S: A222 OK COPY completed
C: A223 COPY 3:200 blurdybloop
S: * NO Disk is 98% full, please delete unnecessary data
S: * NO Disk is never returned with the
BODY fetch, but can be returned with a BODYSTRUCTURE fetch.
Extension data, if present, MUST be in the defined order.

The extension 99% full, please delete unnecessary data of
S: A223 NO COPY failed: disk is full

7.1.3. BAD Response

Contents: OPTIONAL response code
human-readable text

The BAD response indicates an error message from the server. When
tagged, it reports a non-multipart body part are protocol-level error in the
following order:

body MD5
A string giving client's command;
the body MD5 value as defined in [MD5].

body disposition
A parenthesized list with tag indicates the same content and function as command that caused the body disposition for error. The untagged
form indicates a multipart body part.

body language
A string or parenthesized list giving the body language
value as defined in [LANGUAGE-TAGS].

body location
A string list giving protocol-level error for which the body content URI as defined in
[LOCATION].

Any following extension data are associated
command can not yet defined in this
version of the protocol, and would be as described above under
multipart extension data.

ENVELOPE
A parenthesized list that determined; it can also indicate an internal
server failure. The human-readable text describes the envelope structure of condition.

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RFC 3501 IMAPv4 March 2003

Example: C: ...very long command line...
S: * BAD Command line too long
C: ...empty line...
S: * BAD Empty command line
C: A443 EXPUNGE
S: * BAD Disk crash, attempting salvage to a
message. This new disk!
S: * OK Salvage successful, no data lost
S: A443 OK Expunge completed

7.1.4. PREAUTH Response

Contents: OPTIONAL response code
human-readable text

The PREAUTH response is computed by always untagged, and is one of three
possible greetings at connection startup. It indicates that the server
connection has already been authenticated by parsing external means; thus
no LOGIN command is needed.

Example: S: * PREAUTH IMAP4rev1 server logged in as Smith

7.1.5. BYE Response

Contents: OPTIONAL response code
human-readable text

The BYE response is always untagged, and indicates that the
[RFC-2822] header into server
is about to close the component parts, defaulting various
fields as necessary. connection. The fields of human-readable text MAY be
displayed to the envelope structure are user in a status report by the following
order: date, subject, from, sender, reply-to, to, cc, bcc,
in-reply-to, and message-id. The date, subject, in-reply-to,
and message-id fields are strings. client. The from, sender, reply-to,
to, cc, and bcc fields are parenthesized lists of address
structures.

An address structure BYE
response is sent under one of four conditions:

1) as part of a parenthesized list that describes an
electronic mail address. normal logout sequence. The fields of an address structure
are in server will close
the following order: personal name, [SMTP]
at-domain-list (source route), mailbox name, and host name.

[RFC-2822] group syntax is indicated by connection after sending the tagged OK response to the
LOGOUT command.

2) as a special form panic shutdown announcement. The server closes the
connection immediately.

3) as an announcement of
address structure in which an inactivity autologout. The server
closes the host name field is NIL. If connection immediately.

4) as one of three possible greetings at connection startup,
indicating that the
mailbox name field server is also NIL, not willing to accept a
connection from this is an end of group marker client. The server closes the
connection immediately.

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(semi-colon in 67]

RFC 822 syntax). If the mailbox name field is
non-NIL, this is 3501 IMAPv4 March 2003

The difference between a start BYE that occurs as part of group marker, and the mailbox name
field holds the group name phrase.

If the Date, Subject, In-Reply-To, a normal
LOGOUT sequence (the first case) and Message-ID header lines
are absent in the [RFC-2822] header, the corresponding member
of the envelope is NIL; if these header lines are present but
empty the corresponding member a BYE that occurs because of the envelope
a failure (the other three cases) is that the empty
string.

Note: some servers may return a NIL envelope member connection closes
immediately in the
"present but empty" failure case. Clients SHOULD treat NIL and
empty string as identical.

Note: [RFC-2822] requires that In all messages have a valid
Date header. Therefore, cases the date member in client SHOULD
continue to read response data from the envelope can
not be NIL or server until the empty string.

Note: [RFC-2822] requires that the In-Reply-To and
Message-ID headers, if present, have non-empty content.
Therefore, the in-reply-to
connection is closed; this will ensure that any pending untagged
or completion responses are read and message-id members in the
envelope can not be the empty string.

If the From, To, cc, processed.

Example: S: * BYE Autologout; idle for too long

7.2. Server Responses - Server and bcc header lines are absent in the
[RFC-2822] header, or Mailbox Status

These responses are present but empty, the corresponding
member of the envelope always untagged. This is NIL.

If the Sender or Reply-To lines are absent in the [RFC-2822]
header, or how server and mailbox
status data are present but empty, transmitted from the server sets the
corresponding member of the envelope to be the same value as the client. Many of
these responses typically result from member (the client is not expected to know to do
this).

Note: [RFC-2822] requires that all messages have a valid
From header. Therefore, the from, sender, and reply-to
members in the envelope can not be NIL.

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FLAGS
A parenthesized list of flags that are set for this message.

INTERNALDATE
A string representing the internal date of command with the message.

RFC822
Equivalent to BODY[].

RFC822.HEADER
Equivalent to BODY[HEADER]. Note that this did not result in
\Seen being set, because RFC822.HEADER same name.

7.2.1. CAPABILITY Response

Contents: capability listing

The CAPABILITY response data occurs as a result of a FETCH of RFC822.HEADER. BODY[HEADER] response
data occurs as a result of CAPABILITY
command. The capability listing contains a FETCH space-separated
listing of BODY[HEADER] (which sets
\Seen) or BODY.PEEK[HEADER] (which does not set \Seen).

RFC822.SIZE
A number expressing capability names that the [RFC-2822] size of server supports. The
capability listing MUST include the message.

RFC822.TEXT
Equivalent to BODY[TEXT].

UID
A number expressing atom "IMAP4rev1".

In addition, client and server implementations MUST implement the unique identifier of
STARTTLS, LOGINDISABLED, and AUTH=PLAIN (described in [IMAP-TLS])
capabilities. See the message.

Example: S: * 23 FETCH (FLAGS (\Seen) RFC822.SIZE 44827)

7.5. Server Responses - Command Continuation Request

The command continuation request response is indicated by a "+" token
instead of a tag. This form of response Security Considerations section for
important information.

A capability name which begins with "AUTH=" indicates that the
server is
ready to accept supports that particular authentication mechanism.

The LOGINDISABLED capability indicates that the continuation of a LOGIN command from the client. The
remainder of this response is a line of text.

This response is used in
disabled, and that the AUTHENTICATE command to transmit server
data to the client, and request additional client data. This will respond with a tagged NO
response is also used if an argument to any command is a literal.

The client is not permitted attempt to send use the octets of LOGIN command even if the literal unless user
name and password are valid. An IMAP client MUST NOT issue the
LOGIN command if the server indicates advertises the LOGINDISABLED
capability.

Other capability names indicate that it expects it. This permits the server supports an
extension, revision, or amendment to
process commands and reject errors on a line-by-line basis. The
remainder of the command, including IMAP4rev1 protocol.
Server responses MUST conform to this document until the CRLF that terminates client
issues a
command, follows the octets of command that uses the literal. If there associated capability.

Capability names MUST either begin with "X" or be standard or
standards-track IMAP4rev1 extensions, revisions, or amendments
registered with IANA. A server MUST NOT offer unregistered or

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RFC 3501 IMAPv4 March 2003

non-standard capability names, unless such names are prefixed with
an "X".

Client implementations SHOULD NOT require any
additional command arguments capability name
other than "IMAP4rev1", and MUST ignore any unknown capability
names.

A server MAY send capabilities automatically, by using the literal octets are followed
CAPABILITY response code in the initial PREAUTH or OK responses,
and by sending an updated CAPABILITY response code in the tagged
OK response as part of a
space and those arguments.

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Example: C: A001 LOGIN {11}
S: + Ready for additional command text
C: FRED FOOBAR {7}
S: + Ready successful authentication. It is
unnecessary for additional a client to send a separate CAPABILITY command text
C: fat man
S: A001 OK LOGIN completed
C: A044 BLURDYBLOOP {102856} if
it recognizes these automatic capabilities.

Example: S: A044 BAD No such command as "BLURDYBLOOP"

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8. Sample * CAPABILITY IMAP4rev1 connection STARTTLS AUTH=GSSAPI XPIG-LATIN

7.2.2. LIST Response

Contents: name attributes
hierarchy delimiter
name

The following is LIST response occurs as a transcript result of an IMAP4rev1 connection. A long
line in this sample a LIST command. It
returns a single name that matches the LIST specification. There
can be multiple LIST responses for a single LIST command.

Four name attributes are defined:

\Noinferiors
It is broken not possible for editorial clarity.

S: * OK IMAP4rev1 Service Ready
C: a001 login mrc secret
S: a001 OK LOGIN completed
C: a002 select inbox
S: * 18 EXISTS
S: * FLAGS (\Answered \Flagged \Deleted \Seen \Draft)
S: * 2 RECENT
S: * OK [UNSEEN 17] Message 17 any child levels of hierarchy to exist
under this name; no child levels exist now and none can be
created in the future.

\Noselect
It is not possible to use this name as a selectable mailbox.

\Marked
The mailbox has been marked "interesting" by the first unseen message
S: * OK [UIDVALIDITY 3857529045] UIDs valid
S: a002 OK [READ-WRITE] SELECT completed
C: a003 fetch 12 full
S: * 12 FETCH (FLAGS (\Seen) INTERNALDATE "17-Jul-1996 02:44:25 -0700"
RFC822.SIZE 4286 ENVELOPE ("Wed, 17 Jul 1996 02:23:25 -0700 (PDT)"
"IMAP4rev1 WG mtg summary server; the
mailbox probably contains messages that have been added since
the last time the mailbox was selected.

\Unmarked
The mailbox does not contain any additional messages since the
last time the mailbox was selected.

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RFC 3501 IMAPv4 March 2003

If it is not feasible for the server to determine whether or not
the mailbox is "interesting", or if the name is a \Noselect name,
the server SHOULD NOT send either \Marked or \Unmarked.

The hierarchy delimiter is a character used to delimit levels of
hierarchy in a mailbox name. A client can use it to create child
mailboxes, and minutes"
(("Terry Gray" NIL "gray" "cac.washington.edu"))
(("Terry Gray" to search higher or lower levels of naming
hierarchy. All children of a top-level hierarchy node MUST use
the same separator character. A NIL "gray" "cac.washington.edu"))
(("Terry Gray" NIL "gray" "cac.washington.edu"))
((NIL NIL "imap" "cac.washington.edu"))
((NIL NIL "minutes" "CNRI.Reston.VA.US")
("John Klensin" NIL "KLENSIN" "INFOODS.MIT.EDU")) NIL NIL
"<B27397-0100000@cac.washington.edu>")
BODY ("TEXT" "PLAIN" ("CHARSET" "US-ASCII") NIL NIL "7BIT" 3028 92))
S: a003 OK FETCH completed
C: a004 fetch 12 body[header]
S: * 12 FETCH (BODY[HEADER] {350}
S: Date: Wed, 17 Jul 1996 02:23:25 -0700 (PDT)
S: From: Terry Gray <gray@cac.washington.edu>
S: Subject: IMAP4rev1 WG mtg summary and minutes
S: To: imap@cac.washington.edu
S: cc: minutes@CNRI.Reston.VA.US, John Klensin <KLENSIN@INFOODS.MIT.EDU>
S: Message-Id: <B27397-0100000@cac.washington.edu>
S: MIME-Version: 1.0
S: Content-Type: TEXT/PLAIN; CHARSET=US-ASCII
S:
S: )
S: a004 OK FETCH completed
C: a005 store 12 +flags \deleted
S: * 12 FETCH (FLAGS (\Seen \Deleted))
S: a005 OK +FLAGS completed
C: a006 logout
S: * BYE IMAP4rev1 server terminating connection
S: a006 OK LOGOUT completed

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9. Formal Syntax

The following syntax specification uses the Augmented Backus-Naur
Form (ABNF) notation as specified in [ABNF].

In hierarchy delimiter means
that no hierarchy exists; the case of alternative or optional rules in which name is a later rule
overlaps "flat" name.

The name represents an earlier rule, the rule which is listed earlier unambiguous left-to-right hierarchy, and
MUST take
priority. For example, "\Seen" when parsed be valid for use as a flag reference in LIST and LSUB commands.
Unless \Noselect is indicated, the \Seen
flag name and not a flag-extension, even though "\Seen" can be parsed
as a flag-extension. Some, but not all, instances of this rule are
noted below.

Note: [ABNF] rules MUST also be followed strictly; in
particular:

(1) Except valid as noted otherwise, all alphabetic characters
are case-insensitive. The use of upper or lower case
characters to define token strings is an
argument for editorial clarity
only. Implementations MUST commands, such as SELECT, that accept these strings in mailbox names.

Example: S: * LIST (\Noselect) "/" ~/Mail/foo

7.2.3. LSUB Response

Contents: name attributes
hierarchy delimiter
name

The LSUB response occurs as a
case-insensitive fashion.

(2) In all cases, SP refers to exactly one space. result of an LSUB command. It
returns a single name that matches the LSUB specification. There
can be multiple LSUB responses for a single LSUB command. The
data is
NOT permitted to substitute TAB, insert additional spaces,
or otherwise treat SP as being equivalent identical in format to LWSP.

(3) The ASCII NUL character, %x00, MUST NOT be used at any
time.

address = "(" addr-name SP addr-adl SP addr-mailbox SP
addr-host ")"

addr-adl = nstring
; Holds route from [RFC-2822] route-addr if
; non-NIL

addr-host = nstring
; NIL indicates [RFC-2822] group syntax.
; Otherwise, holds [RFC-2822] domain the LIST response.

Example: S: * LSUB () "." #news.comp.mail.misc

7.2.4 STATUS Response

Contents: name

addr-mailbox = nstring
; NIL indicates end
status parenthesized list

The STATUS response occurs as a result of [RFC-2822] group; if
; non-NIL an STATUS command. It
returns the mailbox name that matches the STATUS specification and addr-host is NIL, holds
; [RFC-2822] group name.
; Otherwise, holds [RFC-2822] local-part
; after removing [RFC-2822] quoting
the requested mailbox status information.

Example: S: * STATUS blurdybloop (MESSAGES 231 UIDNEXT 44292)

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RFC 3501 IMAPv4 March 2003

addr-name = nstring
; If non-NIL, holds phrase from [RFC-2822]
; mailbox after removing [RFC-2822] quoting

append = "APPEND" SP mailbox [SP flag-list] [SP date-time] SP
literal

astring = 1*ASTRING-CHAR / string

ASTRING-CHAR = ATOM-CHAR / resp-specials

atom = 1*ATOM-CHAR

ATOM-CHAR = <any CHAR except atom-specials>

atom-specials = "(" / ")" / "{" / SP / CTL / list-wildcards /
quoted-specials / resp-specials

authenticate = "AUTHENTICATE" SP auth-type *(CRLF base64)

auth-type = atom
; Defined by [SASL]

base64 = *(4base64-char) [base64-terminal]

base64-char = ALPHA / DIGIT / "+" / "/"
; Case-sensitive

base64-terminal = (2base64-char "==") / (3base64-char "=")

body = "(" (body-type-1part / body-type-mpart) ")"

body-extension = nstring / number /
"(" body-extension *(SP body-extension) ")"
; Future expansion. Client implementations
; MUST accept body-extension fields. Server
; implementations MUST NOT generate
; body-extension fields except

7.2.5. SEARCH Response

Contents: zero or more numbers

The SEARCH response occurs as defined by
; future standard a result of a SEARCH or standards-track
; revisions UID SEARCH
command. The number(s) refer to those messages that match the
search criteria. For SEARCH, these are message sequence numbers;
for UID SEARCH, these are unique identifiers. Each number is
delimited by a space.

Example: S: * SEARCH 2 3 6

7.2.6. FLAGS Response

Contents: flag parenthesized list

The FLAGS response occurs as a result of a SELECT or EXAMINE
command. The flag parenthesized list identifies the flags (at a
minimum, the system-defined flags) that are applicable for this specification.

body-ext-1part = body-fld-md5 [SP body-fld-dsp [SP body-fld-lang
*(SP body-extension)]]
; MUST NOT be returned
mailbox. Flags other than the system flags can also exist,
depending on non-extensible
; "BODY" fetch

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body-ext-mpart = body-fld-param [SP body-fld-dsp [SP body-fld-lang
*(SP body-extension)]]
; server implementation.

The update from the FLAGS response MUST NOT be returned on non-extensible
; "BODY" fetch

body-fields = body-fld-param SP body-fld-id SP body-fld-desc SP
body-fld-enc SP body-fld-octets

body-fld-desc = nstring

body-fld-dsp = "(" string SP body-fld-param ")" / nil

body-fld-enc = (DQUOTE ("7BIT" / "8BIT" / "BINARY" / "BASE64"/
"QUOTED-PRINTABLE") DQUOTE) / string

body-fld-id = nstring

body-fld-lang = nstring / "(" string *(SP string) ")"

body-fld-loc = nstring

body-fld-lines = recorded by the client.

Example: S: * FLAGS (\Answered \Flagged \Deleted \Seen \Draft)

7.3. Server Responses - Mailbox Size

These responses are always untagged. This is how changes in the size
of the mailbox are transmitted from the server to the client.
Immediately following the "*" token is a number

body-fld-md5 = nstring

body-fld-octets = that represents a
message count.

7.3.1. EXISTS Response

Contents: none

The EXISTS response reports the number

body-fld-param = "(" string SP string *(SP string SP string) ")" / nil

body-type-1part = (body-type-basic / body-type-msg / body-type-text)
[SP body-ext-1part]

body-type-basic = media-basic SP body-fields
; MESSAGE subtype MUST NOT be "RFC822"

body-type-mpart = 1*body SP media-subtype
[SP body-ext-mpart]

body-type-msg = media-message SP body-fields SP envelope
SP body SP body-fld-lines

body-type-text = media-text SP body-fields SP body-fld-lines

capability = ("AUTH=" auth-type) / atom
; New capabilities MUST begin with "X" or be
; registered with IANA of messages in the mailbox.
This response occurs as standard a result of a SELECT or
; standards-track

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capability-data = "CAPABILITY" *(SP capability) SP "IMAP4rev1"
*(SP capability)
; Servers EXAMINE command,
and if the size of the mailbox changes (e.g., new messages).

The update from the EXISTS response MUST implement be recorded by the STARTTLS, AUTH=PLAIN,
; and LOGINDISABLED capabilities
; Servers which offer
client.

Example: S: * 23 EXISTS

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RFC 1730 compatibility MUST
; list "IMAP4" as 3501 IMAPv4 March 2003

7.3.2. RECENT Response

Contents: none

The RECENT response reports the first capability.

CHAR8 = %x01-ff
; any OCTET except NUL, %x00

command = tag SP (command-any / command-auth / command-nonauth /
command-select) CRLF
; Modal based on state

command-any = "CAPABILITY" / "LOGOUT" / "NOOP" / x-command
; Valid in all states

command-auth = append / create / delete / examine / list / lsub /
rename / select / status / subscribe / unsubscribe
; Valid only in Authenticated or Selected state

command-nonauth = login / authenticate / "STARTTLS"
; Valid only when in Not Authenticated state

command-select = "CHECK" / "CLOSE" / "EXPUNGE" / copy / fetch / store /
uid / search
; Valid only when in Selected state

continue-req = "+" SP (resp-text / base64) CRLF

copy = "COPY" SP sequence-set SP mailbox

create = "CREATE" SP mailbox
; Use number of INBOX gives messages with the
\Recent flag set. This response occurs as a NO error

date = date-text / DQUOTE date-text DQUOTE

date-day = 1*2DIGIT
; Day result of month

date-day-fixed = (SP DIGIT) / 2DIGIT
; Fixed-format version a SELECT or
EXAMINE command, and if the size of date-day

date-month = "Jan" / "Feb" / "Mar" / "Apr" / "May" / "Jun" /
"Jul" / "Aug" / "Sep" / "Oct" / "Nov" / "Dec"

date-text = date-day "-" date-month "-" date-year

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date-year = 4DIGIT

date-time = DQUOTE date-day-fixed "-" date-month "-" date-year
SP time SP zone DQUOTE

delete = "DELETE" SP the mailbox
; Use changes (e.g., new
messages).

Note: It is not guaranteed that the message sequence
numbers of INBOX gives recent messages will be a NO error

digit-nz = %x31-39
; 1-9

envelope = "(" env-date SP env-subject SP env-from SP env-sender SP
env-reply-to SP env-to SP env-cc SP env-bcc SP
env-in-reply-to SP env-message-id ")"

env-bcc = "(" 1*address ")" / nil

env-cc = "(" 1*address ")" / nil

env-date = nstring

env-from = "(" 1*address ")" / nil

env-in-reply-to = nstring

env-message-id = nstring

env-reply-to = "(" 1*address ")" / nil

env-sender = "(" 1*address ")" / nil

env-subject = nstring

env-to = "(" 1*address ")" / nil

examine = "EXAMINE" SP contiguous range of
the highest n messages in the mailbox

fetch = "FETCH" SP sequence-set SP ("ALL" / "FULL" / "FAST" /
fetch-att / "(" fetch-att *(SP fetch-att) ")")

fetch-att = "ENVELOPE" / "FLAGS" / "INTERNALDATE" /
"RFC822" [".HEADER" / ".SIZE" / ".TEXT"] /
"BODY" ["STRUCTURE"] / "UID" /
"BODY" [".PEEK"] section ["<" number "." nz-number ">"]

flag = "\Answered" / "\Flagged" / "\Deleted" /
"\Seen" / "\Draft" / flag-keyword / flag-extension
; Does not include "\Recent"

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flag-extension = "\" atom
; Future expansion. Client implementations
; MUST accept flag-extension flags. Server
; implementations MUST NOT generate
; flag-extension flags except as defined (where n is the
value reported by
; future standard or standards-track
; revisions of this specification.

flag-fetch = flag / "\Recent"

flag-keyword = atom

flag-list = "(" [flag *(SP flag)] ")"

flag-perm = flag / "\*"

greeting = "*" SP (resp-cond-auth / resp-cond-bye) CRLF

header-fld-name = astring

header-list = "(" header-fld-name *(SP header-fld-name) ")"

list = "LIST" SP mailbox SP list-mailbox

list-mailbox = 1*list-char / string

list-char = ATOM-CHAR / list-wildcards / resp-specials

list-wildcards = "%" / "*"

literal = "{" number "}" CRLF *CHAR8
; Number represents the number RECENT response). Examples of CHAR8s

lsub = "LSUB" SP mailbox SP list-mailbox

mailbox = "INBOX" / astring
; INBOX
situations in which this is case-insensitive. All not the case variants of
; INBOX (e.g. "iNbOx") MUST are: multiple
clients having the same mailbox open (the first session
to be interpreted notified will see it as INBOX
; not recent, others will
probably see it as an astring. An astring which consists of
; non-recent), and when the case-insensitive sequence "I" "N" "B" "O" "X"
; mailbox is considered
re-ordered by a non-IMAP agent.

The only reliable way to be INBOX and not an astring.
; Refer identify recent messages is to section 5.1 for further
; semantic details of mailbox names.

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mailbox-data = "FLAGS" SP flag-list / "LIST" SP mailbox-list /
"LSUB" SP mailbox-list / "SEARCH" *(SP nz-number) /
"STATUS" SP mailbox SP "("
[status-att SP
look at message flags to see which have the \Recent flag
set, or to do a SEARCH RECENT.

The update from the RECENT response MUST be recorded by the
client.

Example: S: * 5 RECENT

7.4. Server Responses - Message Status

These responses are always untagged. This is how message data are
transmitted from the server to the client, often as a result of a
command with the same name. Immediately following the "*" token is a
number *(SP status-att SP number)] ")" / that represents a message sequence number.

7.4.1. EXPUNGE Response

Contents: none

The EXPUNGE response reports that the specified message sequence
number SP "EXISTS" / has been permanently removed from the mailbox. The message
sequence number SP "RECENT"

mailbox-list = "(" [mbx-list-flags] ")" SP
(DQUOTE QUOTED-CHAR DQUOTE / nil) SP for each successive message in the mailbox

mbx-list-flags = *(mbx-list-oflag SP) mbx-list-sflag
*(SP mbx-list-oflag) /
mbx-list-oflag *(SP mbx-list-oflag)

mbx-list-oflag = "\Noinferiors" / flag-extension
; Other flags; multiple possible per LIST response

mbx-list-sflag = "\Noselect" / "\Marked" / "\Unmarked"
; Selectability flags; only one per LIST response

media-basic = ((DQUOTE ("APPLICATION" / "AUDIO" / "IMAGE" / "MESSAGE" /
"VIDEO") DQUOTE) / string) SP media-subtype
; Defined is
immediately decremented by 1, and this decrement is reflected in [MIME-IMT]

media-message = DQUOTE "MESSAGE" DQUOTE SP DQUOTE "RFC822" DQUOTE
; Defined
message sequence numbers in [MIME-IMT]

media-subtype = string
; Defined subsequent responses (including other
untagged EXPUNGE responses).

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RFC 3501 IMAPv4 March 2003

The EXPUNGE response also decrements the number of messages in [MIME-IMT]

media-text = DQUOTE "TEXT" DQUOTE SP media-subtype
; Defined the
mailbox; it is not necessary to send an EXISTS response with the
new value.

As a result of the immediate decrement rule, message sequence
numbers that appear in [MIME-IMT]

message-data = nz-number SP ("EXPUNGE" / ("FETCH" SP msg-att))

msg-att = "(" (msg-att-dynamic / msg-att-static)
*(SP (msg-att-dynamic / msg-att-static)) ")"

msg-att-dynamic = "FLAGS" SP "(" [flag-fetch *(SP flag-fetch)] ")"
; MAY change for a set of successive EXPUNGE responses
depend upon whether the messages are removed starting from lower
numbers to higher numbers, or from higher numbers to lower
numbers. For example, if the last 5 messages in a 9-message
mailbox are expunged, a "lower to higher" server will send five
untagged EXPUNGE responses for message

msg-att-static = "ENVELOPE" SP envelope / "INTERNALDATE" SP date-time /
"RFC822" [".HEADER" / ".TEXT"] SP nstring /
"RFC822.SIZE" SP number / "BODY" ["STRUCTURE"] SP body /
"BODY" section ["<" sequence number ">"] SP nstring /
"UID" SP uniqueid
; 5, whereas
a "higher to lower server" will send successive untagged EXPUNGE
responses for message sequence numbers 9, 8, 7, 6, and 5.

An EXPUNGE response MUST NOT change for be sent when no command is in
progress, nor while responding to a FETCH, STORE, or SEARCH
command. This rule is necessary to prevent a loss of
synchronization of message

nil = "NIL"

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nstring = string / nil

number = 1*DIGIT
; Unsigned 32-bit integer
; (0 <= n < 4,294,967,296)

nz-number = digit-nz *DIGIT
; Non-zero unsigned 32-bit integer
; (0 < n < 4,294,967,296)

password = astring

quoted = DQUOTE *QUOTED-CHAR DQUOTE

QUOTED-CHAR = <any TEXT-CHAR except quoted-specials> /
"\" quoted-specials

quoted-specials = DQUOTE / "\"

rename = "RENAME" SP mailbox SP mailbox
; Use sequence numbers between client and
server. A command is not "in progress" until the complete command
has been received; in particular, a command is not "in progress"
during the negotiation of INBOX as command continuation.

Note: UID FETCH, UID STORE, and UID SEARCH are different
commands from FETCH, STORE, and SEARCH. An EXPUNGE
response MAY be sent during a destination gives UID command.

The update from the EXPUNGE response MUST be recorded by the
client.

Example: S: * 44 EXPUNGE

7.4.2. FETCH Response

Contents: message data

The FETCH response returns data about a NO error message to the client.
The data are pairs of data item names and their values in
parentheses. This response = *(continue-req / response-data) response-done

response-data = "*" SP (resp-cond-state / resp-cond-bye /
mailbox-data / message-data / capability-data) CRLF

response-done = response-tagged / response-fatal

response-fatal = "*" SP resp-cond-bye CRLF
; Server closes connection immediately

response-tagged = tag SP resp-cond-state CRLF

resp-cond-auth = ("OK" / "PREAUTH") SP resp-text
; Authentication condition

resp-cond-bye = "BYE" SP resp-text

resp-cond-state = ("OK" / "NO" / "BAD") SP resp-text
; Status condition

resp-specials = "]"

resp-text = ["[" resp-text-code "]" SP] text occurs as the result of a FETCH or
STORE command, as well as by unilateral server decision (e.g.,
flag updates).

The current data items are:

BODY
A form of BODYSTRUCTURE without extension data.

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resp-text-code = "ALERT" /
"BADCHARSET" [SP "(" astring *(SP astring) ")" ] /
capability-data / "PARSE" /
"PERMANENTFLAGS" SP "(" [flag-perm *(SP flag-perm)] ")" /
"READ-ONLY" / "READ-WRITE" / "TRYCREATE" /
"UIDNEXT" SP nz-number / "UIDVALIDITY" SP nz-number /
"UNSEEN" SP nz-number /
atom [SP 1*<any TEXT-CHAR except "]">]

search = "SEARCH" [SP "CHARSET" SP astring] 1*(SP search-key)
; CHARSET argument

BODY[<section>]<<origin octet>>
A string expressing the body contents of the specified section.
The string SHOULD be interpreted by the client according to the
content transfer encoding, body type, and subtype.

If the origin octet is specified, this string is a substring of
the entire body contents, starting at that origin octet. This
means that BODY[]<0> MAY be truncated, but BODY[] is NEVER
truncated.

Note: The origin octet facility MUST NOT be registered with IANA

search-key = "ALL" / "ANSWERED" / "BCC" SP astring /
"BEFORE" SP date / "BODY" SP astring /
"CC" SP astring / "DELETED" / "FLAGGED" /
"FROM" SP astring / "KEYWORD" SP flag-keyword / "NEW" /
"OLD" / "ON" SP date / "RECENT" / "SEEN" /
"SINCE" SP date / "SUBJECT" SP astring /
"TEXT" SP astring / "TO" SP astring /
"UNANSWERED" / "UNDELETED" / "UNFLAGGED" /
"UNKEYWORD" SP flag-keyword / "UNSEEN" /
; Above this line were used by a server
in [IMAP2]
"DRAFT" / "HEADER" SP header-fld-name SP astring /
"LARGER" SP number / "NOT" SP search-key /
"OR" SP search-key SP search-key /
"SENTBEFORE" SP date / "SENTON" SP date /
"SENTSINCE" SP date / "SMALLER" SP number /
"UID" SP sequence-set / "UNDRAFT" / sequence-set /
"(" search-key *(SP search-key) ")"

section = "[" [section-spec] "]"

section-msgtext = "HEADER" / "HEADER.FIELDS" [".NOT"] SP header-list /
"TEXT"
; top-level or MESSAGE/RFC822 part

section-part = nz-number *("." nz-number)
; body part nesting

section-spec = section-msgtext / (section-part ["." section-text])

section-text = section-msgtext / "MIME"
; text other than actual body part (headers, etc.)

select = "SELECT" SP mailbox

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seq-number = nz-number / "*"
; message sequence number (COPY, FETCH, STORE
; commands) or unique identifier (UID COPY,
; UID FETCH, UID STORE commands).
; * represents the largest number in use. In
; a FETCH response unless the case of message sequence numbers, client specifically requested
it is
; the number by means of messages in a non-empty mailbox.
; In the case FETCH of unique identifiers, it a BODY[<section>]<<partial>> data
item.

8-bit textual data is the
; unique permitted if a [CHARSET] identifier is
part of the last message body parameter parenthesized list for this section.
Note that headers (part specifiers HEADER or MIME, or the
header portion of a MESSAGE/RFC822 part), MUST be 7-bit; 8-bit
characters are not permitted in headers. Note also that the
; mailbox or, if
[RFC-2822] delimiting blank line between the mailbox is empty, header and the
; mailbox's current UIDNEXT value.
; The server should respond with a tagged BAD
; response to a command that uses a message
; sequence number greater than
body is not affected by header line subsetting; the number blank line
is always included as part of
; messages header data, except in the selected mailbox. This
; includes "*" if the selected mailbox is empty.

seq-range = seq-number ":" seq-number
; two seq-number values and all values between
; these two regardless case
of order.
; Example: 2:4 and 4:2 are equivalent and indicate
; values 2, 3, a message which has no body and 4.
; Example: no blank line.

Non-textual data such as binary data MUST be transfer encoded
into a unique identifer sequence range of
; 3291:* includes textual form, such as BASE64, prior to being sent to the UID of
client. To derive the last message in
; original binary data, the mailbox, even if client MUST
decode the transfer encoded string.

BODYSTRUCTURE
A parenthesized list that value is less than 3291.

sequence-set = (seq-number / seq-range) / *("," sequence-set)
; set of seq-number values, regardless describes the [MIME-IMB] body
structure of order.
; Servers MAY coalesce overlaps and/or execute a message. This is computed by the
; sequence in any order.
; Example: server by
parsing the [MIME-IMB] header fields, defaulting various fields
as necessary.

For example, a simple text message sequence number set of 2,4:7,9,12:*
; for 48 lines and 2279 octets
can have a mailbox with 15 messages body structure of: ("TEXT" "PLAIN" ("CHARSET"
"US-ASCII") NIL NIL "7BIT" 2279 48)

Multiple parts are indicated by parenthesis nesting. Instead
of a body type as the first element of the parenthesized list,
there is equivalent to
; 2,4,5,6,7,9,12,13,14,15
; Example: a message sequence number set of *:4,5:7
; for a mailbox with 10 messages one or more nested body structures. The
second element of the parenthesized list is equivalent to
; 10,9,8,7,6,5,4,5,6,7 and MAY be reordered and
; overlap coalesced to be 4,5,6,7,8,9,10.

status = "STATUS" SP mailbox SP "(" status-att *(SP status-att) ")"

status-att = "MESSAGES" / "RECENT" / "UIDNEXT" / "UIDVALIDITY" /
"UNSEEN"

store = "STORE" SP sequence-set SP store-att-flags

store-att-flags = (["+" / "-"] "FLAGS" [".SILENT"]) SP
(flag-list / (flag *(SP flag))) the multipart
subtype (mixed, digest, parallel, alternative, etc.).

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string = quoted / literal

subscribe = "SUBSCRIBE" SP mailbox

tag = 1*<any ASTRING-CHAR except "+">

text = 1*TEXT-CHAR

TEXT-CHAR = <any CHAR except CR and LF>

time = 2DIGIT ":" 2DIGIT ":" 2DIGIT
; Hours minutes seconds

uid = "UID" SP (copy / fetch / search / store)
; Unique identifiers used instead of

For example, a two part message
; sequence numbers

uniqueid = nz-number
; Strictly ascending

unsubscribe = "UNSUBSCRIBE" SP mailbox

userid = astring

x-command = "X" atom <experimental command arguments>

zone = ("+" / "-") 4DIGIT
; Signed four-digit value consisting of hhmm representing
; hours a text and minutes east of Greenwich (that is,
; the amount that the given time differs from
; Universal Time). Subtracting a
BASE64-encoded text attachment can have a body structure of:
(("TEXT" "PLAIN" ("CHARSET" "US-ASCII") NIL NIL "7BIT" 1152
23)("TEXT" "PLAIN" ("CHARSET" "US-ASCII" "NAME" "cc.diff")
"<960723163407.20117h@cac.washington.edu>" "Compiler diff"
"BASE64" 4554 73) "MIXED")

Extension data follows the timezone
; from multipart subtype. Extension data
is never returned with the given time will give BODY fetch, but can be returned with
a BODYSTRUCTURE fetch. Extension data, if present, MUST be in
the UT form.
; defined order. The Universal Time zone is "+0000".

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10. Author's Note

This document is a revision or rewrite extension data of earlier documents, and
supercedes the protocol specification in those documents: RFC 2060,
RFC 1730, unpublished IMAP2bis.TXT document, RFC 1176, and RFC 1064.

11. Security Considerations

IMAP4rev1 protocol transactions, including electronic mail data, a multipart body part
are
sent in the clear over the network unless protection from snooping following order:

body parameter parenthesized list
A parenthesized list of attribute/value pairs [e.g., ("foo"
"bar" "baz" "rag") where "bar" is
negotiated, either by the use value of STARTTLS, privacy protection "foo", and
"rag" is
negotiated in the AUTHENTICATE command, or some other protection
mechanism is in effect.

11.1. STARTTLS Security Considerations

The specification value of the STARTTLS command and LOGINDISABLED
capability "baz"] as defined in this document replaces that [MIME-IMB].

body disposition
A parenthesized list, consisting of a disposition type
string, followed by a parenthesized list of disposition
attribute/value pairs as defined in [IMAP-TLS]. [IMAP-TLS]
remains normative for the PLAIN [SASL] authenticator.

IMAP client and server implementations MUST implement [DISPOSITION].

body language
A string or parenthesized list giving the
TLS_RSA_WITH_RC4_128_MD5 [TLS] cipher suit, and SHOULD implement body language
value as defined in [LANGUAGE-TAGS].

body location
A string list giving the
TLS_DHE_DSS_WITH_3DES_EDE_CBC_SHA [TLS] cipher suite. This is
important body content URI as it assures that any two compliant implementations can be
configured to interoperate. All other cipher suites defined in
[LOCATION].

Any following extension data are OPTIONAL.
Note that not yet defined in this is a change from section 2.1
version of [IMAP-TLS].

During the [TLS] negotiation, the client MUST check its understanding protocol. Such extension data can consist of the server hostname against the server's identity as presented in
the server Certificate message, in order to prevent man-in-the-middle
attacks. If the match fails, the client SHOULD either ask for
explicit user confirmation,
zero or terminate the connection and indicate
the server's identity is suspect. Matching is performed according more NILs, strings, numbers, or potentially nested
parenthesized lists of such data. Client implementations that
do a BODYSTRUCTURE fetch MUST be prepared to
these rules:

The client accept such
extension data. Server implementations MUST use the server hostname NOT send such
extension data until it used to open the
connection as has been defined by a revision of this
protocol.

The basic fields of a non-multipart body part are in the value to compare against
following order:

body type
A string giving the server content media type name as expressed defined in
[MIME-IMB].

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body subtype
A string giving the server certificate. The client MUST
NOT use any form content subtype name as defined in
[MIME-IMB].

body parameter parenthesized list
A parenthesized list of the server hostname derived from an
insecure remote source (e.g., insecure DNS lookup). CNAME
canonicalization attribute/value pairs [e.g., ("foo"
"bar" "baz" "rag") where "bar" is not done.

If a subjectAltName extension the value of type dNSName "foo" and
"rag" is present in
the certificate, it SHOULD be used as the source value of the
server's identity.

Matching is case-insensitive.

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A "*" wildcard character MAY be used "baz"] as defined in [MIME-IMB].

body id
A string giving the left-most name
component content id as defined in [MIME-IMB].

body description
A string giving the certificate. For example, *.example.com
would match a.example.com, foo.example.com, etc. but would
not match example.com.

If content description as defined in
[MIME-IMB].

body encoding
A string giving the certificate contains multiple names (e.g. more than
one dNSName field), then a match with any one content transfer encoding as defined in
[MIME-IMB].

body size
A number giving the size of the fields body in octets. Note that
this size is considered acceptable.

Both the client size in its transfer encoding and server MUST check not the result
resulting size after any decoding.

A body type of type MESSAGE and subtype RFC822 contains,
immediately after the STARTTLS
command basic fields, the envelope structure,
body structure, and subsequent [TLS] negotiation to see whether acceptable
authentication or privacy was achieved.

11.2. Other Security Considerations size in text lines of the encapsulated
message.

A server error message for an AUTHENTICATE command which fails due to
invalid credentials SHOULD NOT detail why body type of type TEXT contains, immediately after the credentials are
invalid.

Use basic
fields, the size of the LOGIN command sends passwords body in text lines. Note that this
size is the clear. This size in its content transfer encoding and not the
resulting size after any decoding.

Extension data follows the basic fields and the type-specific
fields listed above. Extension data is never returned with the
BODY fetch, but can be
avoided by using the AUTHENTICATE command returned with a [SASL] mechanism
that does not use plaintext passwords, by first negotiating
encryption via STARTTLS or some other protection mechanism.

A server implementation BODYSTRUCTURE fetch.
Extension data, if present, MUST implement a configuration be in which, at the time of authentication, requires that:
(1) defined order.

The STARTTLS command command has been negotiated.
OR
(2) Some other mechanism that protects the session from password
snooping has been provided.
OR
(3) The following measures are in place:
(a) The LOGINDISABLED capability is advertised, and [SASL]
mechanisms (such as PLAIN) which use plaintext passwords extension data of a non-multipart body part are
NOT advertised in the CAPABILITY list.
AND
(b) The LOGIN command returns an error even if the password is
correct.
AND
(c) The AUTHENTICATE command returns an error with all [SASL]
mechanisms which use plaintext passwords, even if the password
is correct.
following order:

body MD5
A server error message for a failing LOGIN command SHOULD NOT specify
that string giving the user name, body MD5 value as opposed to the password, is invalid.

A server SHOULD have mechanisms defined in place to limit or delay failed
AUTHENTICATE/LOGIN attempts. [MD5].

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RFC 3501 IMAPv4 March 2003

Additional security considerations are discussed in the section
discussing

body disposition
A parenthesized list with the AUTHENTICATE same content and LOGIN commands.

12. IANA Considerations

IMAP4 capabilities are registered by publishing function as
the body disposition for a standards track multipart body part.

body language
A string or
IESG approved experimental RFC. The registry is currently located
at:

http://www.iana.org/assignments/imap4-capabilities

As this specification revises parenthesized list giving the STARTTLS and LOGINDISABLED
extensions previously body language
value as defined in [IMAP-TLS], [LANGUAGE-TAGS].

body location
A string list giving the registry will be
updated accordingly.

13. Author's Address

Mark R. Crispin
Networks and Distributed Computing
University body content URI as defined in
[LOCATION].

Any following extension data are not yet defined in this
version of Washington
4545 15th Avenue NE
Seattle, WA 98105-4527

Phone: (206) 543-5762

EMail: MRC@CAC.Washington.EDU

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Appendices

A. References the protocol, and would be as described above under
multipart extension data.

ENVELOPE
A parenthesized list that describes the envelope structure of a
message. This is computed by the server by parsing the
[RFC-2822] header into the component parts, defaulting various
fields as necessary.

The following documents contain definitions or specifications which fields of the envelope structure are necessary to understand this document properly:

[ABNF] Crocker, D., in the following
order: date, subject, from, sender, reply-to, to, cc, bcc,
in-reply-to, and Overell, P. "Augmented BNF for Syntax
Specifications: ABNF", RFC 2234, November 1997.

[ANONYMOUS] Newman, C. "Anonymous SASL Mechanism", RFC 2245, November
1997.

[CHARSET] Freed, N., message-id. The date, subject, in-reply-to,
and Postel, J. "IANA Character Set Registration
Procedures", RFC 2978, October 2000.

[DIGEST-MD5] Leach, P., message-id fields are strings. The from, sender, reply-to,
to, cc, and Newman, C. "Using Digest Authentication
as bcc fields are parenthesized lists of address
structures.

An address structure is a SASL Mechanism", RFC 2831, May 2000.

[DISPOSITION] Troost, R., Dorner, S., and Moore, K. "Communicating
Presentation Information in Internet Messages: parenthesized list that describes an
electronic mail address. The
Content-Disposition Header", RFC 2183, August 1997.

[IMAP-TLS] Newman, C. "Using TLS with IMAP, POP3 and ACAP", RFC 2595,
June 1999.

[KEYWORDS] Bradner, S. "Key words for use fields of an address structure
are in RFCs to Indicate
Requirement Levels", RFC 2119, Harvard University, March 1997.

[LANGUAGE-TAGS] Alvestrand, H. "Tags for the Identification of
Languages", RFC 1766, March 1995.

[LOCATION] Palme, J., Hopmann, A., and Shelness, N. "MIME
Encapsulation following order: personal name, [SMTP]
at-domain-list (source route), mailbox name, and host name.

[RFC-2822] group syntax is indicated by a special form of Aggregate Documents, such as HTML (MHTML)",
address structure in which the host name field is NIL. If the
mailbox name field is also NIL, this is an end of group marker
(semi-colon in RFC
2557, March 1999.

[MD5] Myers, J., 822 syntax). If the mailbox name field is
non-NIL, this is a start of group marker, and Rose, M. "The Content-MD5 Header Field", RFC
1864, October 1995.

[MIME-HDRS] Moore, K. "MIME (Multipurpose Internet Mail Extensions)
Part Three: Message Header Extensions for Non-ASCII Text", RFC 2047,
November 1996.

[MIME-IMB] Freed, N., the mailbox name
field holds the group name phrase.

If the Date, Subject, In-Reply-To, and Borenstein, N. "MIME (Multipurpose Internet
Mail Extensions) Part One: Format Message-ID header lines
are absent in the [RFC-2822] header, the corresponding member
of