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Network Working Group Greg Vaudreuil
Internet Draft Octel Network Services
Expires: 6/16/95 January 24, October 20, 1995 April 20, 1995
Enhanced Mail System Status Codes
<draft-ietf-notary-status-01.txt>
Changes from Last Version
1) Numerious editiorial corrections and clarifications including a revised
overview section.
2) Several new error codes were added.
a) An additional status code was added for mailbox valid. It was
suggested that other mailbox status was too ambigious for use in a
positive delivery report.
b) An additional status code was added to indicate that the address
has changed and no forwarding address is available.
c) An additional status code was added to indicate that a conversion
required for delivery failed.
3) The BNF was updated more clearly express the allowable values for each
of the status code fields. The first digit was redefined to have the same
values as the SMTP error codes, values 2-Success, 4-Persistant temporary
failure, and 5-Permanant failure. This change was discussed and agreed to
in San Jose but was overlooked in the first ID posting.
1.
<draft-ietf-notary-status-02.txt>
Status of this Memo
This document is an Internet-Draft. Internet-Drafts are working
documents of the Internet Engineering Task Force (IETF), its areas,
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 and may be updated, replaced, or obsoleted by other documents
at any time. It is inappropriate to use Internet- Drafts as
reference material or to cite them other than as "work in progress."
To learn the current status of any Internet-Draft, please check the "1id-
abstracts.txt"
"1id-abstracts.txt" listing contained in the Internet- Drafts Shadow
Directories on ds.internic.net (US East Coast), nic.nordu.net
(Europe), ftp.isi.edu (US West Coast), or munnari.oz.au (Pacific
Rim).Introduction
Internet Draft Mail System Status Codes January 24, April 20, 1995
2.
1. Overview
There currently is not a standard mechanism for the reporting of
mail system errors except for the limited set offered by SMTP and
the system specific text descriptions sent in mail messages. There
is a pressing need for a rich machine readable status code for use
in delivery status notifications [2]. [DSN]. This document proposes a
new set of status codes for this purpose.
SMTP [1] [SMTP] error codes have historically been used for reporting
mail system errors. Because of limitations in the SMTP code design,
these are not suitable for use in delivery status notifications.
SMTP provides about 12 useful codes for delivery reports. The
majority of the codes are protocol specific response codes such as
the 354 response to the SMTP data command. Each of the 12 useful
codes are each overloaded to indicate several error conditions each.
SMTP suffers some scars from history, most notably the unfortunate
damage to the reply code extension mechanism by uncontrolled use.
This proposal facilitates future extensibility by requiring the
client to interpret unknown error codes according to the theory of
codes while requiring servers to register new response codes.
The SMTP theory of reply codes partitioned in the number space such
a manner that the remaining available codes will not provide the
space needed. The most critical example is the existence of only 5
remaining codes for mail system errors. The mail system
classification includes both host and mailbox error conditions. The
remaining third digit space will would be completely consumed as needed
to indicate MIME and media conversion errors and security system
errors.
A revision to the SMTP theory of reply codes to better distribute
the error conditions in the number space will necessarily be
incompatible with SMTP. Further, consumption of the remaining
reply-code number space for delivery notification reporting will
reduce the available codes for new ESMTP extensions.
The following proposal starts from is based on the SMTP theory of reply codes.
It adopts the success, permanent error, and transient error
semantics of the first value, with a further description and
classification in the second. This proposal re-distributes the
classifications to better distribute the error conditions, such as
separating mailbox from host errors. The detail
value has been separated by a period and replaced by a two digit integer.
This separation into an integer provides a virtually unbounded space for
future growth as well as visually indicates that the codes is not SMTP.
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3.
2. Status Codes
This document defines a new set of status codes to report delivery status
in the DSN. mail
system conditions. These status codes are intended to be used for
media and language independent status reporting and reporting. They are not
intended for system specific diagnostics.
The syntax of the new status codes is defined as:
status-code = class "." subject "." detail
class = "2"/"4"/"5"
subject = 2*digit 1*3digit
detail = 2*digit
The status codes 1*3digit
White-space characters and comments are explicit enumeration's NOT allowed within a status-
code. Each numeric sub-code within the status-code MUST be
expressed without leading zero digits.
Status codes consist of each three numerical fields separated by ".". The
first sub-code indicates whether the delivery attempt was
successful. The second sub-code indicates the probable source of
any delivery anomalies, and the three fields. third sub-code indicates a precise
error condition.
The codes space defined is intended to be extensible only by
standards track documents. Mail system specific status codes should
be mapped as
closely close as possible to the standard status codes.
Servers should send only defined, registered status codes. System
specific errors and diagnostics may should be carried in the DSN via protocol specific extension fields. by means other
than status codes. Clients should preserve the extensibility of the
code space by reporting the general error described in the second protocol digit subject
sub-code when the specific detail is unrecognized.
The first digit class sub-code provides a broad classification of the status.
The enumerated values of this first digit the class are defined as:
2.X.X Success (2)
Success specifies that the DSN is reporting a positive delivery
action. Detail digits sub-codes may provide notification of
transformations required for delivery.
4.X.X Persistent Transient Failure (4)
A persistent transient failure is one in which the message as
sent is valid, but some temporary event prevents the successful
sending of the message. Sending in the future may be successful.
5.X.X Permanent Failure (5)
A permanent failure is one which is not likely to be resolved by
resending the message in the current form. Some change to the
message or the destination must be made for successful delivery.
A client must recognize and report based on the first digit even where
subsequent digits are unrecognized.
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A client must recognize and report class sub-code even where
subsequent subject sub-codes are unrecognized.
The second subject digit sub-code classifies the status. This digit value applies to
each of the three classifications. The second digit, subject sub-code, if
recognized, must be reported even if the additional detail provided
by the third digit detail sub-code is not recognized. The enumerated values for
the second digit subject sub-code are:
X.0.X Other or undefined status (0) Undefined Status
There is no additional subject information available.
X.1.X Addressing Status
The address status (1) reports on the originator or destination
address. It may include address syntax or validity. These
errors can generally be corrected by the sender and retried.
X.2.X Mailbox Status
Mailbox status (2) indicates that something having to do with the
mailbox has cause this DSN. Mailbox issues are assumed to be
under the general control of the recipient.
X.3.X Mail System Status
Mail system status (3) indicates that something having to do with the
destination system has caused this DSN. System issues are
assumed to be under the general control of the destination system
administrator.
X.4.X Network and Routing Status (4)
The networking or routing codes report status about the delivery
system itself. These system components include any necessary
infrastructure such as directory and routing services. Network
issues are assumed to be under the control of the destination or
intermediate system administrator.
X.5.X Mail Delivery Protocol Status (5)
The mail delivery protocol status codes report failures involving
the message delivery protocol. These failures include the full
range of problems resulting from implementation errors or an
unreliable connection. Mail delivery protocol issues may be
controlled by many parties including the originating system,
destination system, or intermediate system administrators.
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X.6.X Message Content or Media Status (6)
The message content or media status codes report failures
involving the content of the message. These codes report
failures due to translation, transcoding, or otherwise
unsupported message media. Message content or media issues are
under the control of both the sender and the receiver, both of
whom must support a common set of supported content-types.
X.7.X Security or Policy Status (7)
The detail value provides more information about the security or policy status codes report failures involving
policies such as per-recipient or per-host filtering and is defined
relative
cryptographic operations. Security and policy status issues are
assumed to be under the subject control of either or both the status as indicated by sender and
recipient. Both the second digit. sender and recipient must permit the
exchange of messages and arrange the exchange of necessary keys
and certificates for cryptographic operations.
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4. Enumberated
3. Enumerated Status Codes
The following section defines and describes the detail sub-code. The
detail value provides more information about the status code digits.
4.1 and is
defined relative to the subject of the status.
3.1 Other or Undefined Status (0)
There is no additional detail available for other or
X.0.0 Other undefined Status
Other undefined status
codes. The is the only detail digit defined undefined error code. It
should be used for all errors for which only the class of the
error is (0).
4.2 known.
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3.2 Address Status (1)
The address status reports on the specified address. It may include
address syntax or validity.
4.2.1
X.1.0 Other Address Status (1.0)
Something about the address specified in the message caused this
DSN.
4.2.2
X.1.1 Bad destination mailbox address (1.1)
The mailbox specified in the address does not exist. For domain
names, this means the address portion to the left of the "@" sign
is invalid. This code is only useful for permanent failures.
4.2.3
X.1.2 Bad destination system address (1.2)
The destination system specified in the address does not exist or
is incapable of accepting mail. For domain names, this means the
address portion to the right of the "@" is invalid for mail.
This codes is only useful for permanent failures.
4.2.4
X.1.3 Bad destination mailbox address syntax (1.3)
The destination address was syntactically invalid. This can
apply to any field in the address. This code is only useful for
permanent failures.
4.2.5 Mailbox
X.1.4 Destination mailbox address ambiguous (1.4)
The mailbox address as specified matches one or more recipients
on the destination system. This may result if a heuristic
address mapping algorithm is used to map the specified address to
a local mailbox name.
This code is only useful for permanent failures.
4.2.6 Address
X.1.5 Destination address Valid (1.5)
This mailbox address as specified was valid. This status code
should be used for positive delivery reports.
4.2.7 Mailbox
X.1.6 Destination mailbox has moved, No forwarding address (1.6)
The mailbox address is was valid but is not longer availableresident on longer available
resident on the system. This code is only useful for permanent
failures.
X.1.7 Bad senders mailbox address syntax
The senders address was syntactically invalid. This can apply to
any field in the address.
X.1.8 Bad senders system address
The senders system specified in the address does not exist or is
incapable of accepting return mail. For domain names, this means
the
system. This code address portion to the right of the "@" is only useful invalid for permanent failures. mail.
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4.3
3.3 Mailbox Status (2)
Mailbox status indicates that something having to do with the mailbox has
cause this DSN. Mailbox issues are assumed to be under the general control
of the individual recipient.
4.3.1
X.2.0 Other or undefined mailbox status (2.0)
The mailbox exists, but something about the destination mailbox
has caused the sending of this DSN.
4.3.2
X.2.1 Mailbox disabled, not accepting messages (2.1)
The mailbox exists, but is not accepting messages. This may be a
permanent error if the mailbox will never be re-enabled or a
transient error if the mailbox is only temporarily disabled.
4.3.3
X.2.2 Mailbox full (2.2)
The mailbox is full either because the user has exceeded an
administrative
quota or the dedicated physical resources have been exceeded. quota. The general semantics implies that the
recipient can delete messages to make more space available. This
code should be used as a persistent transient failure.
4.3.4
X.2.3 Message length exceeds administrative limit (2.3)
A per-mailbox administrative message length limit has been
exceeded. This status code should be used when the per-mailbox
message length limit is less than the general system limit. This
code should be used as a permanent failure.
4.3.5
X.2.4 Mailing list expansion problem (2.4)
The mailbox is a mailing list address and the mailing list was
unable to be expanded. This code may represent a permanent
failure or a persistent transient failure.
4.3.6
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Internet Draft Mail System Status (3)
System status indicates that something having to do with the destination
system has caused this DSN. System issues are assumed to be under the
general control of the Codes April 20, 1995
3.4 Mail system administrator.
4.3.7 status
X.3.0 Other or undefined mail system status (3.0)
The destination system exists and normally accepts mail, but
something about the system has caused the generation of this DSN.
4.3.8
X.3.1 Mail System full (3.1)
System
Mail system storage has been exceeded. The general semantics
imply that the individual recipient may not be able to delete
material to make room for additional messages. This is useful
only as a persistent transient error.
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4.3.9
X.3.2 System not accepting network messages (3.2)
The host on which the mailbox is resident is not accepting
messages. Examples of such conditions include an immanent shutdown
shutdown, excessive load, or system maintenance. This is useful
for both permanent and permanent transient errors.
4.3.10
X.3.3 System not capable of selected features (3.3)
Selected message features specified for the message are not supported by
the destination system. This is useful only as a permanent error.
4.3.11 can occur in gateways when features
from one domain cannot be mapped onto the supported feature in
another.
X.3.4 Message too big for system (3.4)
The message is larger than per-message size limit. This limit
may either be for physical or administrative reasons. This is
useful only as a permanent error.
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4.4
3.5 Network and Routing Status (4)
The networking or routing codes report status about the delivery system
itself, both the network and intermediate processing.
4.4.1
X.4.0 Other or undefined network or routing status (4.0)
Something went wrong with the networking, but it is not clear
what the problem is, or the problem cannot be well expressed with
any of the other provided detail codes.
4.4.2
X.4.1 No answer from host (4.1)
The outbound connection attempt was not answered, either because
the remote system was busy, or otherwise unable to take a call.
This is useful only as a persistent transient error.
4.4.3
X.4.2 Bad connection (4.2)
The outbound connection was completed, established, but was otherwise unable
to complete the message transaction, either because of time-out, excessive packet loss,
or inadequate connection quality. This is useful only as a
persistent transient error.
4.4.4 Routing
X.4.3 Directory server failure (4.3)
The network system was unable to determine the next hop for forward the message, because a nameserver
directory server was unavailable to resolve the address or provide a
route. unavailable. This is useful only as a
persistent transient error.
4.4.5
The inability to connect to an Internet DNS server is one example
of the directory server failure error.
X.4.4 Unable to route (4.4)
The network mail system was unable to determine the next hop for the
message because the necessary routing information was unavailable
from the routing directory server. This is useful for both permanent and
persistent transient errors.
4.4.6 Network
A DNS lookup returning only an SOA (Start of Administration)
record for a domain name is one example of the unable to route
error.
X.4.5 Mail system congestion (4.5)
The network or mail system was unable to deliver the message because the network
was congested, or the queuing
mail system was overfilled. congested. This is useful only as a persistent
transient error.
4.4.7
X.4.6 Routing loop detected (4.6)
A routing loop caused the message to be forwarded too many times,
either because of incorrect routing tables or a user forwarding
loop. This is useful only as a persistent transient error.
4.4.8
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X.4.7 Delivery time expired (4.7)
The message was considered too old by the rejecting system,
either because it remained on that host too long or because the TTL
time-to-live value specified by the sender of the message was
exceeded. This is useful only as a persistent transient error.
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4.5
3.6 Mail Delivery Protocol Status (5)
4.5.1
X.5.0 Other or undefined protocol status (0)
Something was wrong with the protocol necessary to deliver the
message to the next hop and the problem cannot be well expressed
with any of the other provided detail codes.
4.5.2
X.5.1 Invalid command (5.1)
A mail transaction protocol command was issued which was either
out of sequence or otherwise unsupported. This is useful only as a
permanent error.
4.5.3
X.5.2 Syntax error (5.2)
A mail transaction protocol command was issued which could not be
interpreted, either because the syntax was wrong or the command was not supported.
is unrecognized. This is useful only as a permanent error.
4.5.4
X.5.3 Too many recipients (5.3)
More recipients were specified for the message than could have
been delivered by the protocol. This error should normally
result in the segmentation of the message into two, the remainder
of the recipients to be delivered on a subsequent delivery
attempt. It is included in this list in the event that such
segmentation is not possible. This is useful only as a
permanent error.
4.5.5
X.5.4 Invalid command arguments (5.4)
A valid mail transaction protocol command was issued with invalid
arguments, either because the arguments were out of range or
represented unrecognized features. This is useful only as a
permanent error.
4.5.6
X.5.5 Wrong protocol version (5.5)
A protocol version mis-match existed which could not be
automatically resolved by downgrading one of the communicating
parties. This should never happen in ESMTP. This is useful only as a permanent error.
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4.6
3.7 Message Content or Message Media Status (6)
4.6.1
X.6.0 Other or undefined media error (6.0)
Something about the content of a message caused it to be
considered undeliverable and the problem cannot be well expressed
with any of the other provided detail codes.
4.6.2
X.6.1 Media not supported (6.1)
The media of the message is not supported by the either the
delivery protocol or a host in the forwarding path. This is
useful only as a permanent error.
4.6.3
X.6.2 Conversion required and prohibited (6.2)
The content of the message must be converted before it can be
delivered and such conversion is not permitted. Such
prohibitions may be the expression of the sender in the message
itself or the policy of the sending host. This
is useful only as a permanent error.
4.6.4
X.6.3 Conversion required but not supported (6.3)
The message content must be converted to be forwarded but such
conversion is not possible or is not practical by a host in the
forwarding path. This condition may result when a relay supports
ESMTP transport but not MIME downgrade. This is useful only as a permanent error.
4.6.5
X.6.4 Conversion with loss performed (6.4)
This is a warning sent to the sender when message delivery was
successfully but when the delivery required a conversion in which
some data was lost.
This is useful only for successful notification.
4.6.6
X.6.5 Conversion Failed (6.5)
A conversion was required but was unsucessful. unsuccessful. This may be
useful as a
permanant permanent or persistant persistent temporary notification.
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4.7
3.8 Security or Policy Status (7)
4.7.1
X.7.0 Other or undefined security status (7.0)
Something related to security caused the message to be returned,
and the problem cannot be well expressed with any of the other
provided detail codes. This status code may also be used when
the condition cannot be further described because of security
policies in force.
4.7.2
X.7.1 Delivery not authorized, message refused (7.1)
The sender is not authorized to send to the destination. This
can be the result of per-host or per-recipient filtering. This
memo does not discuss the merits of any such filtering, but
provides a mechanism to report such. This is useful only as a
permanent error.
4.7.3
X.7.2 Mailing list expansion prohibited (7.2)
The sender is not authorized to send a message to the intended
mailing list. This is useful only as a permanent error.
4.7.4
X.7.3 Security conversion required but not possible (7.3)
A conversion from one secure messaging protocol to another was
required for delivery and such conversion was not possible. This
is useful only as a permanent error.
4.7.5
X.7.4 Security features not supported (7.4)
A message contained security features such as secure
authentication which could not be supported on the delivery
protocol. This is useful only as a permanent error.
4.7.6
X.7.5 Cryptographic failure (7.5)
A transport system otherwise authorized to validate or decrypt a
message in transport was unable to do so because necessary
information such as key was not available or such information was
invalid. This is useful only as a permanent error.
4.7.7
X.7.6 Cryptographic algorithm not supported (7.6)
A transport system otherwise authorized to validate or decrypt a
message was unable to do so because the necessary algorithm was
not supported. This
is useful only as a permanent error.
4.7.8
X.7.7 Message integrity failure (7.7)
A transport system otherwise authorized to validate a message was
unable to do so because the message was corrupted or altered.
This may be useful as a permanent, transient persistent, or
successful delivery code.
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5.
4. References
[RFC-821]
[SMTP] Postel, J., "Simple Mail Transfer Protocol", STD 10, RFC 821,
USC/Information Sciences Institute, August 1982.
6.
[DSN] Moore, K., Vaudreuil, G., "An Extensible Message Format for
Delivery Status Notifications", Internet-Draft.
5. Security Consideration
This document describes a status code system with increased
precision. Use of these status codes may disclose additional
information about how an internal mail system is implemented beyond
that currently available.
6. Acknowledgments
The author wishes to offer special thank Harald Alvestrand, Marko
Kaittola, and Keith Moore for their extensive review and
constructive suggestions.
7. Author's Address
Gregory M. Vaudreuil
Octel Network Services
17060 Dallas Parkway
Suite 214
Dallas, TX 75248-1905
214-733-2722
Greg.Vaudreuil@ons.octel.com
Voice/Fax: +1-214-733-2722
Greg.Vaudreuil@Octel.com
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8. Appendix - Collected Status Codes
X.1.0 Other Address Status
X.1.1 Bad destination mailbox address
X.1.2 Bad destination system address
X.1.3 Bad destination mailbox address syntax
X.1.4 Mailbox Destination mailbox address ambiguous
X.1.5 Mailbox Destination mailbox address valid
X.1.6 Mailbox has moved
X.1.7 Bad senders mailbox address syntax
X.1.8 Bad senders system address
X.2.0 Other or undefined mailbox status
X.2.1 Mailbox disabled, not accepting messages
X.2.2 Mailbox full
X.2.3 Message length exceeds administrative limit.
X.2.4 Mailing list expansion problem
X.3.0 Other or undefined mail system status
X.3.1 System Mail system full
X.3.2 System not accepting network messages
X.3.3 System not capable of selected features
X.3.4 Message too big for system
X.4.0 Other or undefined network or routing status
X.4.1 No answer from host
X.4.2 Bad connection
X.4.3 Routing server failure
X.4.4 Unable to route
X.4.5 Network congestion
X.4.6 Routing loop detected
X.4.7 Delivery time expired
X.5.0 Other or undefined protocol status
X.5.1 Invalid command
X.5.2 Syntax error
X.5.3 Too many recipients
X.5.4 Invalid command arguments
X.5.5 Wrong protocol version
X.6.0 Other or undefined media error
X.6.1 Media not supported
X.6.2 Conversion required and prohibited
X.6.3 Conversion required but not supported
X.6.4 Conversion with loss performed
X.6.5 Conversion failed
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X.7.0 Other or undefined security status
X.7.1 Delivery not authorized, message refused
X.7.2 Mailing list expansion prohibited
X.7.3 Security conversion required but not possible
X.7.4 Security features not supported
X.7.5 Cryptographic failure
X.7.6 Cryptographic algorithm not supported
X.7.7 Message integrity failure
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9. Appendix - Existing SMTP Reply-Codes From RFC 821
211 System status, or system help reply
214 Help message
[Information on how to use the receiver or the meaning of a
particular non-standard command; this reply is useful only
to the human user]
220 <domain> Service ready
221 <domain> Service closing transmission channel
250 Requested mail action okay, completed
251 User not local; will forward to <forward-path>
354 Start mail input; end with <CRLF>.<CRLF>
421 <domain> Service not available,
closing transmission channel
[This may be a reply to any command if the service knows it
must shut down]
450 Requested mail action not taken: mailbox unavailable
[E.g., mailbox busy]
451 Requested action aborted: local error in processing
452 Requested action not taken: insufficient system storage
500 Syntax error, command unrecognized
[This may include errors such as command line too long]
501 Syntax error in parameters or arguments
502 Command not implemented
503 Bad sequence of commands
504 Command parameter not implemented
550 Requested action not taken: mailbox unavailable
[E.g., mailbox not found, no access]
551 User not local; please try <forward-path>
552 Requested mail action aborted: exceeded storage allocation
553 Requested action not taken: mailbox name not allowed
[E.g., mailbox syntax incorrect]
554 Transaction failed
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