WDIFF

draft-kille-mixer-rfc1327bis-00.txt --> draft-kille-mixer-rfc1327bis-01.txt

Network Working S.E. Kille
Group ISODE Consortium
INTERNET-DRAFT June August 1995
Expires: December 1995 February 1996
File: draft-kille-mixer-rfc1327bis-01.txt

MIXER (Mime Internet X.400 Enhanced Relay):

Mapping between X.400 and RFC 822/MIME

<draft-kille-mixer-rfc1327bis-00.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. Internet Drafts may be
updated, replaced, or obsoleted by other documents at any time. It is
not appropriate to use Internet Drafts as reference material or to
cite them other than as a ``working draft'' or ``work in progress.''
Please check the I-D abstract listing contained in each Internet Draft
directory to learn the current status of this or any other Internet
Draft.

NOTE: This document (version 2.2) is change-barred relative to RFC 1327. version
2.1. Some obvious formatting errors have been introducted by this
process, and these will not be present in the final version.

Network Working Group S.E. Kille
Internet Draft ISODE Consortium
RFC 1327bis June August 1995
Obsoletes: RFCs 987, 1026, 1138, 1148, 1327, 1495
Updates: RFC 822
|

MIXER (Mime Internet X.400 Enhanced Relay): |

Mapping between X.400 and RFC 822/MIME |

Status of this Memo: |

This document describes a set of mappings which will enable |
interworking between systems operating the CCITT X.400 |
Recommendations on Message Handling Systems (1984, 1988 and |
1992 versions) / ISO IEC 10021 Message Oriented Text |
Interchange Systems (MOTIS) , [2,13,15], and systems using the
RFC 822 | mail protocol [21] [16] or protocols derived from RFC
822, | supplemented by the MIME specifications [14]. [9]. Older
systems | which do not use MIME are still supported. The
approach aims to maximise the services offered across the
boundary, whilst not requiring unduly complex mappings. The
mappings should not require any changes to end systems. This
document is a revision based on the evolving sequence of
RFCs 987, 1026, 1138, 1148 and 1327 [22,23,25-27], [17,18,20-22], which it
obsoletes. It | incorporates changes specified in RFC 1495 [10],
[5], which it | also obsoletes.

This document specifies a mapping between two families of |
protocols, which includes both protocol/service mappings and |
use of a mandatory global mappings. This specification
should be used when this mapping is performed on the DARPA
Internet or in the UK Academic Community. performed. This |
specification may be modified in the light of implementation
experience, but no substantial changes are expected.

This draft document will be submitted to the RFC editor as
a protocol specification. Distribution of this memo is
unlimited. Please send comments to the author.

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2 - Service Elements .............................. 16
2.1 - The Notion of Service Across a Gateway ........ 16
2.2 - RFC 822 ....................................... 17
2.3 - X.400 ......................................... 23 24
3 - Basic Mappings ................................ 34 35
3.1 - Notation ...................................... 34 35
3.2 - ASCII and IA5 ................................. 36 37
3.3 - Standard Types ................................ 36 37
3.4 - Encoding ASCII in Printable String ............ 39 40
3.5 41 - RFC 1522 ...................................... | 42
4 - Addressing and 42ssage Message IDs .................... | 43
4.1 - A textual representation of MTS.ORAddress ..... 43 44
4.2 50 - .mc | ......................................... | Global Address Mapping ........................ 51
4.3 - EBNF.822-address <-> MT53ORAddress MTS.ORAddress ............ | 54
4.4 - Repeated Mappings ............................. 67
4.5 - Directory Names ............................... 69
4.6 - MTS Mappings .................................. 70
4.7 - IPMS Mappings ................................. 75
5 - Detailed Mappings ............................. 81
5.1 - .mc | ..81..................................... |

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5.1 - RFC 822 -> X.400: Detailed Mappings ........... 81
5.2 - Return of Contents ............................ 100 101
5.3 - .mc | ..101.................................... | X.400 -> RFC 822: Detailed Mappings ........... 102
Appendix A - Mappings Specific to SMTP ..................... 139
6 - Probes .139.................................... | ........................................ 139
7 - Long Lines .139................................ | .................................... 139
8 - SMTP Extensions .139........................... | ............................... 139
8.1 - SMTP Extension mapping to X.400 .139........... | ............... 139
8.2 - X.400 Mapping to SMTP Extensions .140.......... | .............. 140
Appendix B - Mapping with X.400(1984) .141............. | ................. 141
Appendix C - RFC 822 Extensions for X.400 access 143........ | [
Appendix D - Object Identifier Assignment .................. 144 144............... [
Appendix E - BNF Summary .............................. ................................... 145
Appendix F - Format of address mapping tables .............. 156
1 - Global Mapping Information .................... 156
2 - Mechanisms to register and to distribute |
Mapping Rules 156........................................... | .............................................. 156
3 - Syntax Definitions ............................ 157
4 - Table Lookups ................................. 158
5 - Domain -> O/R Address format .................. 159
6 - O/R Address -> Domain format .................. 159
7 - Domain -> O/R Address of Gateway table ........ 160
Appendix G - Conformance 161................................ | ................................... 161
Appendix H - Change History: RFC 987, 1026, 1138, 1148 |
............................................................ 163
1 - Introduction .................................. 163
2 - Service Elements .............................. 163
3 - Basic Mappings ................................ 164
4 - Addressing .................................... 164
5 - Detailed Mappings ............................. 164
6 - Appendices .................................... 165
Appendix I - Change History: RFC 1148 to RFC 1327 166....... | .......... 166
1 - General ....................................... 166
2 - Basic Mappings ................................ 166
3 - Addressing .................................... 166
4 - Detailed Mappings ............................. 167
5 - Appendices .................................... 167
Appendix J - Change History: RFC 1327 to this Document |
168......................................................... |
............................................................ 168
1 - General 168.................................... | ....................................... 168
2 - Service Elements 168........................... | .............................. 168
3 - Basic Mappings 168............................. | ................................ 168
4 - Addressing 168................................. | .................................... 168
5 - Detailed Mappings 169.......................... |
6 - Appendices 169................................. | ............................. 169

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6 - Appendices .................................... 169

Kille [page 4]

Table of Contents

1 - Overview ...................................... 6
1.1 - X.400 ......................................... 6
1.2 - .mc | ......6.................................. | RFC 822 and MIME .............................. 6
1.3 - The need for conversion ....................... 7
1.4 - General approach .............................. 7
1.5 - Gatewaying Model .............................. 8
1.6 - X.400 (1984) .................................. 11
1.7 - .mc | .....11.................................. | X.400 (1992) .................................. 12
1.8 - MIME .....12................................... | .......................................... 12
1.9 - Body Parts .....12............................. | .................................... 12
1.10 - .mc .......................................... Compatibility with previous versions ......... 13
1.11 - Aspects not covered .......................... 13 ......13.................. [
1.12 - Subsetting ................................... 13
1.13 - .mc | .....13................................. ......14................................ |
1.14 - .mc .......................................... 14
1.15 - Document Structure ........................... 14
1.16 - Acknowledgements ............................. 14 15
2 - Service Elements .............................. 16
2.1 - The Notion of Service Across a Gateway ........ 16
2.2 - RFC 822 ....................................... 17
2.3 - X.400 ......................................... 23 24
3 - Basic Mappings ................................ 34 35
3.1 - Notation ...................................... 34 35
3.2 - ASCII and IA5 ................................. 36 37
3.3 - Standard Types ................................ 36 37
3.4 - Encoding ASCII in Printable String ............ 39 40
3.5 41 - RFC 1522 ...................................... | 42
4 - Addressing and 42ssage Message IDs .................... | 43
4.1 - A textual representation of MTS.ORAddress ..... 43 44
4.2 50 - .mc | ......................................... | Global Address Mapping ........................ 51
4.3 - EBNF.822-address <-> MT53ORAddress MTS.ORAddress ............ | 54
4.4 - Repeated Mappings ............................. 67
4.5 - Directory Names ............................... 69
4.6 - MTS Mappings .................................. 70
4.7 - IPMS Mappings ................................. 75
5 - Detailed Mappings ............................. 81
5.1 - .mc | ..81..................................... |

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6 - Appendices .................................... 169

Kille [page 4]

Chapter 1 -- Overview

1.1. X.400

This document relates primarily to the ITU 1988 and 1992 X.400 |
Series Recommendations / ISO IEC 10021 on the Message Oriented |
Text Interchange Service (MOTIS). This ISO/ITU standard is |
referred to in this document as "X.400", which is a convenient |
shorthand. Any reference to the 1984 ITU Recommendations will be |
explicit. Any mappings relating to elements which are in the |
1992 version and not in the 1988 version will be noted |
explicitly. X.400 defines an Interpersonal Messaging System |
(IPMS), making use of a store and forward Message Transfer |
System. This document relates to the IPMS, and not to wider |
application of X.400. X.400, such as EDI as defined in X.435.

1.2. | RFC 822 and MIME

RFC 822 evolved as a messaging standard on the DARPA (the US
Defense Advanced Research Projects Agency) Internet. RFC 822 |
specifies an end to end message format, consisting of a header |
and an unstructured text body. MIME (Multipurpose Internet Mail |
Extensions) specifies a structured message body format for use |
with RFC 822. The term "RFC 822" is used in this document to |
refer to the combination of MIME and RFC 822. RFC 822 and MIME |
are used in conjunction with a number of different message |
transfer protocol environments. The core of the MIXER |
specification is designed to work with any supporting message |
transfer protocol. |

One transfer protocol, SMTP, is of particular importance and |
is covered in MIXER. On the Internet and other TCP/IP networks, |
RFC 822 is used in conjunction with |
RFC 821, also known as Simple Mail Transfer Protocol (SMTP)
[35],
[31], in a manner conformant with the host requirements |
specification . [10]. Use of MIXER with SMTP is defined in
Appendix A. |

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1.3. The need for conversion

There is a large community using RFC 822 based protocols for mail
services, who will wish to communicate with users of the IPMS
provided by X.400 systems. This will also be a requirement in
cases where communities intend to make a transition to use of an
X.400 IPMS, as conversion will be needed to ensure a smooth
service transition. It is expected that there will be more than
one gateway, and this specification will enable them to behave in
a consistent manner. Note that the term gateway is used to
describe a component performing the protocol mappings between RFC
822 and X.400. This is standard usage amongst mail implementors,
but should be noted carefully by transport and network service
implementors.

Consistency between gateways is desirable to provide:

1. Consistent service to users.

2. The best service in cases where a message passes through
multiple gateways.

1.4. General approach

There are a number of basic principles underlying the details of
the specification. These principles are goals, and are not
achieved in all aspects of the specification.

1. The specification should be pragmatic. There should not be
a requirement for complex mappings for "Academic" reasons.
Complex mappings should not be required to support trivial
additional functionality.

2. Subject to 1), functionality across a gateway should be as
high as possible.

3. It is always a bad idea to lose information as a result of
any transformation. Hence, it is a bad idea for a gateway
to discard information in the objects it processes. This
includes requested services which cannot be fully mapped.

4. All mail gateways actually operate at exactly one level
above the layer on which they conceptually operate. This
implies that the gateway must not only be cognisant of the

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semantics of objects at the gateway level, but also be
cognisant of higher level semantics. If meaningful
transformation of the objects that the gateway operates on
is to occur, then the gateway needs to understand more than
the objects themselves.

5. Subject to 1), the specification should be reversible. That
is, a double transformation should bring you back to where
you started.

1.5. Gatewaying Model

1.5.1. X.400

X.400 defines the IPMS Abstract Service in X.420/ISO 10021-7 ,
[16]
[11] which comprises of three basic services:

1. Origination

2. Reception

3. Management

Management is a local interaction between the user and the IPMS,
and is therefore not relevant to gatewaying. The first two
services consist of operations to originate and receive the
following two objects:

1. IPM (Interpersonal Message). This has two components: a
heading, and a body. The body is structured as a sequence
of body parts, which may be basic components (e.g., IA5 |
text, or G3 fax), or Interpersonal Messages. The heading
consists of fields containing end to end user information,
such as subject, primary recipients (To:), and importance.

2. IPN (Inter Personal Notification). A notification about
receipt of a given IPM at the UA level.

The Origination service also allows for origination of a probe,
which is an object to test whether a given IPM could be correctly
received.

The Reception service also allows for receipt of Delivery Reports
(DR), which indicate delivery success or failure.

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These IPMS Services utilise the Message Transfer (MT)
Abstract Service [17]. [12]. The MT Abstract Service provides the
following three basic services:

1. Submission (used by IPMS Origination)

2. Delivery (used by IPMS Reception)

3. Administration (used by IPMS Management)

Administration is a local issue, and so does not affect this
standard. Submission and delivery relate primarily to the MTS
Message (comprising Envelope and Content), which carries an IPM
or IPN (or other uninterpreted contents). There is also an
Envelope, which includes an ID, an originator, and a list of
recipients. Submission also includes the probe service, which
supports the IPMS Probe. Delivery also includes Reports, which
indicate whether a given MTS Message has been delivered or not.

The MTS is REFINED into provided by MTAs which interact using the MTA |
(Message Transfer Agent) Service, which defines the interaction
between MTAs, along with the procedures for distributed
operation. This service provides for transfer of MTS Messages,
Probes, and Reports.

1.5.2. RFC 822

RFC 822 is based on the assumption that there is an underlying
service, which is here called the 822-MTS service. The 822-MTS
service provides three basic functions:

1. Identification of a list of recipients.

2. Identification of an error return address.

3. Transfer of an RFC 822 message.

It is possible to achieve 2) within the RFC 822 header. Some
822-MTS protocols, in particular SMTP, can provide additional
functionality, but |

This specification will be used most commonly with SMTP as these are neither mandatory in SMTP, nor
available in other |
the 822-MTS protocols, they are service. The core MIXER specification is written so |
that it does not considered
here. Details rely on non-basic 822-MTS services. Use of aspects specific to two |
non-basic SMTP services is described in Appendix A. The core of |
this document is written using SMTP terminology for 822-MTS protocols are
given |

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services, for clarity in Appendices B and C. its usual domain of application. |

An RFC 822 message consists of a header, and content which
is uninterpreted ASCII text. The header is divided into fields,
which are the protocol elements.

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analogous to P2 heading fields, although some are analogous to
MTS Service Elements or MTA Service Elements. |

RFC 822 supports delivery status notifications by use of the |
NOTARY mechanisms [33]. [29].

1.5.3. The Gateway

Given this functional description of the two services, the
functional nature of a gateway can now be considered. It would |
be elegant to consider the 822-MTS SMTP (822-MTS) service mapping onto
the MTS Service Elements and RFC 822 mapping onto an IPM, but
reality just does not fit. Another elegant approach would be to
treat this document as the definition of an X.400 Access Unit
(AU). Again, reality does not fit. It is necessary to consider
that the IPM format definition, the IPMS Service Elements, the
MTS Service Elements, and MTA Service Elements on one side are |
mapped into RFC 822 + 822-MTS SMTP on the other in a slightly tangled
manner. The details of the tangle will be made clear in Chapter
5. Access to the MTA Service Elements is minimised.

The following basic mappings are thus defined. When going
from RFC 822 to X.400, an RFC 822 message and the associated SMTP |
822-MTS
information is always mapped into an IPM (MTA, MTS, and | IPMS
Services) and a Delivery Status Notification is mapped onto | a
Report. Going from X.400 to RFC 822, an RFC 822 message and the |
associated 822-MTS SMTP information may be derived from:

1. An IPN (MTA, MTS, and IPMS services) |

2. An IPM (MTA, MTS, and IPMS services)

A Report (MTA, and MTS Services) is mapped onto a delivery status |
notification. |

Probes (MTA Service) must be processed by the gateway, as
discussed in Chapter 5. MTS Messages containing Content Types
other than those defined by the IPMS are not mapped by the
gateway, and should be rejected at the gateway. |

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This specification is concerned with X.400 IPMS. Future |
specifications may defined mappings for other X.400 content |
types.

1.5.4. Repeated Mappings

The primary goal of this specification is to support single

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mappings, so that X.400 and RFC 822 users can communicate with
maximum functionality.

The mappings specified here are designed to work where a
message traverses multiple times between X.400 and RFC 822. This
is often essential, particularly in the case of distribution
lists. However, in general, this will lead to a level of service
which is the lowest common denominator (approximately the
services offered by RFC 822).

Some RFC 822 networks may wish to use X.400 as an
interconnection mechanism (typically for policy reasons), and
this is fully supported.

Where an X.400 message transfers to RFC 822 and then back to |
X.400, there is no expectation of X.400 services which do not
have an equivalent service in standard RFC 822 being preserved -
although this may be possible in some cases.

1.6. X.400 (1984)

Much of this work is based on the initial specification of RFC
987 and in its addendum RFC 1026, which defined a mapping between
X.400(1984) and RFC 822. A basic decision is that the mapping
defined in this document is to the full 1988 version of X.400,
and not to a 1984 compatible subset. New features of X.400(1988)
can be used to provide a much cleaner mapping than that defined
in RFC 987. This is important, to give good support to
communities which will utilise full X.400 at an early date. To |
interwork with 1984 systems, Appendix B shall be followed.

If a message is being transferred to an X.400(1984) system
by way of X.400(1988) MTA it will give a slightly better service |
to follow the rules of Appendix B, than to downgrade without this |
knowledge. Downgrading specifications which supplement those |
specified in X.400 are given in RFC 1328 and RFC 1496 (HARPOON) |
[11,28].

1.7. |
X.400 (1992) |
[6,23].

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1.7. X.400 (1992)

X.400 (1992) features are not used by the core of this mapping, |
and so there is not an equivalent downgrade problem. |

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1.8. MIME |

MIME format messages are generated by this mapping. As MIME |
messages are fully RFC 822 compliant, this will not cause |
problems with systems which are not MIME capable. |

1.9. Body Parts |

MIME and X.400 IPMS can both carry arbitrary body parts. This |
specification describes mapping of the framework for structured |
messages, but does not specify how specific body parts shall be |
mapped. Body part mapping is an open ended problem, as new body |
parts (attachments) will continue to be added to both X.400 and |
MIME. |

MIME defines a mechanism for adding new body parts, and new |
body parts are registered with the IANA. |

X.400 defines a mechanism adding new body parts, usually |
referred to as Body Part 15. Extensions are defined by Object |
Identifiers, so there is no requirement for a body part |
registration authority. The Electronic Mail Association (EMA) |
maintains a list of some commonly used body parts. The EMA has |
specified a mechanism to use the File Transfer Body Part (FTBP) |
as a more generic means to support message attachments. This |
approach is gaining widespread commercial support. MIXER defines |
how to map between MIME and both the Body Part 15 and EMA/FTBP |
extension mechanisms for X.400. In many cases, this will enable |
a gateway implementor to map between the same body part carried |
by these mechanisms. |

Mapping of standard IPM and MIME body parts, and some |
extended MIME and X.400 body parts, is defined in RFC 1494bis |
[12].
[7]. This also gives a model for specifying further mappings. |

It will not be possible to specify all mappings. Therefore, |
MIXER defines encapsulation mechanisms for both MIME and X.400. |
This will allow all body parts to be transferred end to end, |
irrespective of a mapping being defined. |

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To provide a gateway service, it is therefore necessary for |
an implementation to conform to both this specification and to |
provide various body part mappings, such as those defined in RFC |
1494bis. |

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1.10. Compatibility with previous versions

The changes between this and older versions of the document are
given in Appendices H, I and J. These are RFCs 987, 1026, |
1138, 1148 and 1148. 1327. This document is a revision of RFC 1148 [26]. 1327 . [
As far as possible, changes have been made in a compatible [
fashion. [

1.11. Aspects not covered [

There have been a number of cases where previous version versions of this |
document | were used in a manner which was not intended. This |
section is to make clear some limitations of scope. In
particular, this specification does not specify:

- Extensions of RFC 822 to provide access to all X.400
services

- X.400 user interface definition *

These are really coupled. To map the X.400 services, this |
specification defines a number of extensions to RFC 822. As a
side effect, these give the 822 user access to SOME X.400
services. However, the aim on the RFC 822 side is to preserve
current service, and it is intentional that access is not given
to all X.400 services. Thus, it will be a poor choice for X.400
implementors to use MIXER as an interface - there are too many |
aspects of X.400 which cannot be accessed through it. If a text
interface is desired, a specification targeted at X.400, without
RFC 822 restrictions, would be more appropriate. Some optional
and limited extensions in this area have proved useful, and are |
defined in Appendix C.

1.12. Subsetting

This proposal specifies a mapping which is appropriate to
preserve services in existing RFC 822 communities.
Implementations and specifications which subset this |
specification are non-conformant and strongly discouraged.

1.13. |
Related Specifications |

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1.13. |
Specification Language |

ISO and Internet standards have clear definitions as to the style |
of language used. This specification maps between ISO/ITU |
protocol and Internet protocols. This document uses ISO |
terminology for the following reasons: |

1. This was done in previous versions. |

2. ISO language may be mechanically converted to Internet |
language, but not vice versa. |

To interpet this document according to Internet rules, replace |
every occurrence of "shall" with "must". |

1.14.
Related Specifications

Mappings between Mail-11 and X.400 and Mail-11 and rfc822 are |
described in RFC1405, using mappings related to those defined |
here [8]. |

1.14. [3].

1.15. Document Structure

This document has five chapters:

1. Overview - this chapter.

2. Service Elements - This describes the (end user) services
mapped by a gateway.

3. Basic mappings - This describes some basic notation used in
Chapters 3-5, the mappings between character sets, and some
fundamental protocol elements.

4. Addressing - This considers the mapping between X.400 O/R
names and RFC 822 addresses, which is a fundamental gateway
component.

5. Detailed Mappings - This describes the details of all other
mappings.

There are also ten appendices. |

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WARNING:
THE REMAINDER OF THIS SPECIFICATION IS TECHNICALLY DETAILED.
IT WILL NOT MAKE SENSE, EXCEPT IN THE CONTEXT OF RFC 822 AND
X.400 (1988). DO NOT ATTEMPT TO READ THIS DOCUMENT UNLESS
YOU ARE FAMILIAR WITH THESE SPECIFICATIONS.

1.15.

1.16. Acknowledgements

The work in this specification was substantially based on RFC 987
and RFC 1148, which had input from many people, who are credited
in the respective documents.

A number of comments from people on RFC 1148 lead to RFC |
1327. In particular, there were comments and suggestions from:
Maurice Abraham (HP); Harald Alvestrand (Sintef); Peter Cowen

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(X-Tel); Jim Craigie (JNT); Ella Gardner (MITRE); Christian |
Huitema (Inria); Erik Huizer (SURFnet); Neil Jones (DEC); Ignacio
Martinez (IRIS); Julian Onions (X-Tel); Simon Poole (SWITCH);
Clive Roberts (Data General); Pete Vanderbilt (SUN); Alan Young
(Concurrent). |

RFC 1327 has been widely adopted, and a review team was |
formed. This comprised of: Urs Eppenberger (SWITCH)(Chair); |
Claudio Allocchio (INFN); Harald Alvestrand (UNINETT); Dave |
Crocker (Brandenburg); Ned Freed (Innosoft); Erik Huizer |
(SURFnet); Steve Kille (ISODE Consortium); Peter Sylvester |
(EdelWeb) |

Harald Alvestrand also supplied the tables mapping DSN |
status codes with X.400 codes. Ned Freed defined parts of the |
File Transfer Body Part mapping. |

Comment and input has also been received from: Samir |
Albadine (Transpac); Jacqui Caren | (Cray); Allan Cargille (MCI); |
Kevin Carrosso (Innosoft); Eamon Doyle (Isocor); Jeroun | Houttin
(Terena); Jyrki Heikkinen (ICL); Kevin Jordan (CDS); Paul |
Kingsnorth (DEC); Carl-Uno Manros (Manros Consulting); Robert |
Miles (Softswitch); Michel Musy (Bull); Kenji Nonaka (NTT): Tom |
Oliphant (SWITCH); Julian Onions (NEXOR); Mary la Roche |
(Citicorp); Eftimios Tsigros (Universite Libre de Bruxelles); |
David Wilson (ISODE Consortium); Alan Young (ISODE Consortium); |

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Chapter 2 - Service Elements

This chapter considers the services offered across a gateway
built according to this specification. It gives a view of the
functionality provided by such a gateway for communication with
users in the opposite domain. This chapter considers service
mappings in the context of SINGLE transfers only, and not
repeated mappings through multiple gateways.

2.1. The Notion of Service Across a Gateway

RFC 822 and X.400 provide a number of services to the end user.
This chapter describes the extent to which each service can be
supported across an X.400 <-> RFC 822 gateway. The cases
considered are single transfers across such a gateway, although
the problems of multiple crossings are noted where appropriate.

2.1.1. Origination of Messages

When a user originates a message, a number of services are
available. Some of these imply actions (e.g., delivery to a
recipient), and some are insertion of known data (e.g.,
specification of a subject field). This chapter describes, for
each offered service, to what extent it is supported for a
recipient accessed through a gateway. There are three levels of
support:

Supported
The corresponding protocol elements map well, and so the
service can be fully provided.

Not Supported
The service cannot be provided, as there is a complete
mismatch.

Partial Support
The service can be partially fulfilled.

In the first two cases, the service is simply marked as
"Supported" or "Not Supported". Some explanation may be given if
there are additional implications, or the (non) support is not
intuitive. For partial support, the level of partial support is

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summarised. Where partial support is good, this will be
described by a phrase such as "Supported by use of.....". A
common case of this is where the service is mapped onto a non-
standard service on the other side of the gateway, and this would
have lead to support if it had been a standard service. In many
cases, this is equivalent to support. For partial support, an
indication of the mechanism is given, in order to give a feel for
the level of support provided. Note that this is not a
replacement for Chapter 5, where the mapping is fully specified.

If a service is described as supported, this implies:

- Semantic correspondence.

- No (significant) loss of information.

- Any actions required by the service element.

An example of a service gaining full support: If an RFC 822
originator specifies a Subject: field, this is considered to be
supported, as an X.400 recipient will get a subject indication.

In many cases, the required action will simply be to make the
information available to the end user. In other cases, actions
may imply generating a delivery report.

All RFC 822 services are supported or partially supported
for origination. The implications of non-supported X.400
services is described under X.400.

2.1.2. Reception of Messages

For reception, the list of service elements required to support
this mapping is specified. This is really an indication of what
a recipient might expect to see in a message which has been
remotely originated.

2.2. RFC 822

RFC 822 does not explicitly define service elements, as distinct
from protocol elements. However, all of the RFC 822 header
fields, with the exception of trace, can be regarded as
corresponding to implicit RFC 822 service elements.

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2.2.1. Origination in RFC 822

A mechanism of mapping, used in several cases, is to map the RFC
822 header into a heading extension in the IPM (InterPersonal
Message). This can be regarded as partial support, as it makes
the information available to any X.400 implementations which are
interested in these services. Communities which require
significant RFC 822 interworking are recommended to require that
their X.400 User Agents are able to display these heading
extensions. Support for the various service elements (headers)
is now listed.

Date:
Supported.

From:
Supported. For messages where there is also a sender field,
the mapping is to "Authorising Users Indication", which has
subtly different semantics to the general RFC 822 usage of
From:.

Sender:
Supported.

Reply-To:
Supported.

To: Supported.

Cc: Supported.

Bcc: Supported.

Message-Id:
Supported.

In-Reply-To:
Supported, for a single reference. Where multiple
references are given, partial support is given by mapping to
"Cross Referencing Indication". This gives similar
semantics.

References:
Supported.

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Keywords:
Supported by use of a heading extension.

Subject:
Supported.

Comments:
Supported by use of a heading extension. |

Encrypted:
Supported by use of a heading extension.

Resent-*
Supported by use of a heading extension. Note that
addresses in these fields are mapped onto text, and so are
not accessible to the X.400 user as addresses. In
principle, fuller support would be possible by mapping onto
a forwarded IP Message, but this is not suggested.

Other Fields
In particular X-* fields, and "illegal" fields in common
usage (e.g., "Fruit-of-the-day:") are supported by use of
heading extensions. |

MIME introduces the following headings, which are supported as |
follows: |

Content-Type: |
Supported. The definition of MIME Content Type is somewhat |
like X.400 Encoded Information Type, but has some aspects |
of X.400 Content Type. The mapping is complex, but it will |
either be mapped to an equivalent X.400 piece of information |
or tunnelled by use of a special extended body part defined |
in RFC 1494. 1494bis. |

Content-Transfer-Encoding: |
Supported. The encoding of the information in X.400 will be |
appropriate to the data being transferred. The service is |
mapped in an appropriate manner. |

Content-ID: |
Supported in some cases. Support depend on the body part |
and the mapping selected by the gateway. |

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Content-Description: |
Supported in some cases. Support depend on the body part |
and the mapping selected by the gateway. |

MIME-Version: |
Supported by use of a heading extension. |

MIME, like RFC 822, does not explicitly define services. It is |
useful in the service section to note support for MIME Content |
types that do not map directly to atomic body parts: |

multipart/mixed |
Supported. |

multipart/alternative |
Partially supported. No data is lost. The fact that the |
body parts are alternatives is indicated in a heading |
extension, and there is no guarantee that this can be |
interpreted by an X.400 user agent, and by a subject line. |

multipart/digest |
Supported. |

multipart/parallel |
Partially supported. Not No data is lost. The fact that the |
body parts are parallel is indicated in a heading extension, |
which may not be interpreted by an X.400 user agent, and by |
a subject line. |

multipart/unknown |
Supported. Unknown semantics are not mapped. |

message/rfc822 |
Supported. |

message/partial |
Supported by mapping of message fragments to X.400 messages. |
X.400 User Agents will not in general be able to |
automatically reassemble fragments. |

message/external-body |
Supported by incorporating the external body into the X.400 |
message. |

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message/unknown |
Supported. Unknown semantics are not mapped.

other |

otherSupport

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Support for the other MIME content types (text, application, |
image, audio, video) is defined in RFC 1494. 1494bis, with a |
fallback mechanism for undefined an unrecognised types |
defined in MIXER.

2.2.2. Reception by RFC 822

This considers reception by an RFC 822 User Agent of a message
originated in an X.400 system and transferred across a gateway.
The following standard services (headers) may be present in such
a message:

Date:

From:

Sender:

Reply-To:

To:

Cc:

Bcc:

Message-Id:

In-Reply-To:

References:

Subject:

Content-Type: |

Content-Transfer-Encoding: |

MIME-Version: |

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The following non-standard services (headers) may be present in |
the header of a message. These are defined in more detail in
Chapter 5 (5.3.4, 5.3.6, 5.3.7):

Autoforwarded:

Autosubmitted: |

X400-Content-Identifier: |

Content-Language: |

Conversion:

Conversion-With-Loss:

Delivery-Date:

Discarded-X400-IPMS-Extensions:

Discarded-X400-MTS-Extensions:

DL-Expansion-History:

Deferred-Delivery:

Expiry-Date:

Importance:

Incomplete-Copy:

Latest-Delivery-Time: *

Message-Type:

Obsoletes:

Original-Encoded-Information-Types:

Originator-Return-Address:

Priority:

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Reply-By:

Requested-Delivery-Method:

Sensitivity:

X400-Content-Type:

X400-MTS-Identifier:

X400-Originator:

X400-Received:

X400-Recipients:

2.3. X.400

2.3.1. Origination in X.400

When mapping services from X.400 to RFC 822 which are not
supported by RFC 822, new RFC 822 headers are defined. defined, and |
registered by publication in this standard. It is intended that these fields will be registered, and that co-
operating |
co-operating RFC 822 systems may also use them. Where these new
fields are used, and no system action is implied, the service can
be regarded as being partially supported. Chapter 5 describes
how to map X.400 services onto these new headers. Other elements
are provided, in part, by the gateway as they cannot be provided
by RFC 822.

Some service elements are marked N/A (not applicable).
There are five cases, which are marked with different comments:

N/A (local)
These elements are only applicable to User Agent / Message
Transfer Agent interaction and so they cannot apply to RFC
822 recipients.

N/A (PDAU)
These service elements are only applicable where the
recipient is reached by use of a Physical Delivery Access
Unit (PDAU), and so do not need to be mapped by the gateway.

N/A (reception)

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These services are only applicable for reception.

N/A (prior)
If requested, this service must be performed prior to the
gateway.

N/A (MS)
These services are only applicable to Message Store (i.e., a
local service).

Finally, some service elements are not supported. In
particular, the new security services are not mapped onto RFC
822. Unless otherwise indicated, the behaviour of service
elements marked as not supported will depend on the criticality
marking supplied by the user. If the element is marked as
critical for transfer or delivery, a non-delivery notification
will be generated. Otherwise, the service request will be
ignored.

2.3.1.1. Basic Interpersonal Messaging Service

These are the mandatory IPM services as listed in Section 19.8 of
X.400 / ISO/IEC 10021-1, listed here in the order given. Section
19.8 has cross references to short definitions of each service.

Access management
N/A (local).

Content Type Indication
Supported by a new RFC 822 header (Content-Type:). (X400-Content-Type:). |

Converted Indication
Supported by a new RFC 822 header (X400-Received:).

Delivery Time Stamp Indication
N/A (reception).

IP Message Identification
Supported.

Message Identification
Supported, by use of a new RFC 822 header
(X400-MTS-Identifier). This new header is required, as
X.400 has two message-ids whereas RFC 822 has only one (see |

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IP Message Identification

Non-delivery Notification
Not supported in all cases. Supported where the recipient |
system supports NOTARY DSNs. In general all RFC 822 systems |
will return error reports by use of IP messages. In other
service elements, this pragmatic result can be treated as
effective support of this service element.

Original Encoded Information Types Indication
Supported as a new RFC 822 header
(Original-Encoded-Information-Types:).

Submission Time Stamp Indication
Supported.

Typed Body
The mapping of ForwardedIPMessage and IA5 body parts is |
defined and supported. A framework form mapping other body |
parts, including encapsulation mechanism is defined. |
Mapping of standard body parts and selected other body parts |
is defined in RFC 1494bis.

User Capabilities Registration
N/A (local).

2.3.1.2. IPM Service Optional User Facilities

This section describes support for the optional (user selectable)
IPM services as listed in Section 19.9 of X.400 / ISO/IEC 10021-
1, listed here in the order given. Section 19.9 has cross
references to short definitions of each service.

Additional Physical Rendition
N/A (PDAU).

Alternate Recipient Allowed
Not supported. There is no RFC 822 service equivalent to
prohibition of alternate recipient assignment (e.g., an RFC
822 system may freely send an undeliverable message to a
local postmaster). Thus, the gateway cannot prevent
assignment of alternative recipients on the RFC 822 side.
This service really means giving the user control as to
whether or not an alternate recipient is allowed. This

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specification requires transfer of messages to RFC 822
irrespective of this service request, and so this service is
not supported.

Authorising User's Indication
Supported.

Auto-forwarded Indication
Supported as new RFC 822 header (Auto-Forwarded:).

Basic Physical Rendition
N/A (PDAU).

Blind Copy Recipient Indication
Supported.

Body Part Encryption Indication
Supported by use of a new RFC 822 header
(Original-Encoded-Information-Types:), although in most
cases it will not be possible to map the body part in
question.

Content Confidentiality
Not supported.

Content Integrity
Not supported.

Conversion Prohibition
Supported
Supported. Operation defined in line with RFC 1494. 1494bis. |

Conversion Prohibition in Case of Loss of Information
Supported
Supported. Operation defined in line with RFC 1494. 1494bis. |

Counter Collection
N/A (PDAU).

Counter Collection with Advice
N/A (PDAU).

Cross Referencing Indication
Supported.

Deferred Delivery

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N/A (prior). This service should always be provided by the
MTS prior to the gateway. A new RFC 822 header
(Deferred-Delivery:) is provided to transfer information on
this service to the recipient.

Deferred Delivery Cancellation
N/A (local).

Delivery Notification
Supported. This is performed at the gateway, but may be |
performed at the end system if the end system supports |
NOTARY. Thus, a notification is sent by the gateway to the
originator. If the 822-MTS protocol is JNT Mail, a
notification may also be sent by the recipient UA. *

Delivery via Bureaufax Service
N/A (PDAU).

Designation of Recipient by Directory Name
N/A (local).

Disclosure of Other Recipients
Supported by use of a new RFC 822 header (X400-Recipients:).
This is descriptive information for the RFC 822 recipient,
and is not reverse mappable.

DL Expansion History Indication
Supported by use of a new RFC 822 header
(DL-Expansion-History:).

DL Expansion Prohibited
Distribution List means MTS supported distribution list, in
the manner of X.400. This service does not exist in the RFC
822 world. RFC 822 distribution lists should be regarded in |
X.400 terms as an informal redistribution mechanism, beyond
the scope of this control. Messages will be sent to RFC 822, 822 |
distribution lists, irrespective of whether this service is |
requested. Theoretically therefore, this service is |
supported, although in practice it may appear that it is not supported.

Express Mail Service
N/A (PDAU).

Expiry Date Indication

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no automatic action can be expected.

Explicit Conversion
N/A (prior).

Forwarded IP Message Indication
Supported, with some loss
Supported. |

Grade of information. The message Delivery Selection
Not Supported. There is
forwarded no equivalent service in an RFC 822 body, and so can only be interpreted
visually.

Grade of Delivery Selection
N/A (PDAU)

Importance Indication
Supported as new RFC 822. |

Importance Indication
Supported as new RFC 822 header (Importance:).

Incomplete Copy Indication
Supported as new RFC 822 header (Incomplete-Copy:).

Language Indication
Supported as new RFC 822 header (Language:).

Latest Delivery Designation
Not supported. A new RFC 822 header (Latest-Delivery-Time:)
is provided, which may be used by the recipient.

Message Flow Confidentiality
Not supported.

Message Origin Authentication
N/A (reception).

Message Security Labelling
Not supported.

Message Sequence Integrity
Not supported.

Multi-Destination Delivery
Supported.

Multi-part Body
Supported. |

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Non Receipt Notification Request
Not supported.

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Non Repudiation of Delivery
Not supported.

Non Repudiation of Origin
N/A (reception).

Non Repudiation of Submission
N/A (local).

Obsoleting Indication
Supported as new RFC 822 header (Obsoletes:).

Ordinary Mail
N/A (PDAU).

Originator Indication
Supported.

Originator Requested Alternate Recipient
Not supported, but is placed as comment next to address
(X400-Recipients:).

Physical Delivery Notification by MHS
N/A (PDAU).

Physical Delivery Notification by PDS
N/A (PDAU).

Physical Forwarding Allowed
Supported by use of a comment in a new RFC 822 header
(X400-Recipients:), associated with the recipient in
question.

Physical Forwarding Prohibited
Supported by use of a comment in a new RFC 822 header
(X400-Recipients:), associated with the recipient in
question.

Prevention of Non-delivery notification
Supported,
Supported where SMTP and NOTARY are available. In other |
cases formally supported, as delivery notifications cannot |
be generated by RFC 822. In practice, errors will be
returned as IP

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Primary and Copy Recipients Indication
Supported

Probe
Supported at the gateway (i.e., the gateway services the
probe).

Probe Origin Authentication
N/A (reception).

Proof of Delivery
Not supported.

Proof of Submission
N/A (local).

Receipt Notification Request Indication
Not supported. |

Redirection Allowed Disallowed by Originator |
Redirection means MTS supported redirection, in the manner
of X.400. This service does not exist in the RFC 822 world.
RFC 822 redirection (e.g., aliasing) should be regarded as
an informal redirection mechanism, beyond the scope of this
control. Messages will be sent to RFC 822, irrespective of |
whether this service is requested. Theoretically therefore, In practice, control of |
this service is supported, although in practice it may
appear that it is not supported.

Registered Mail
N/A (PDAU).

Registered Mail to Addressee in Person
N/A (PDAU).

Reply Request Indication
Supported as comment next to address.

Replying IP Message Indication
Supported.

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Report Origin Authentication
N/A (reception).

Request for Forwarding Address

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N/A (PDAU).

Requested Delivery Method
N/A (local). The services required must be dealt with at
submission time. Any such request is made available through
the gateway by use of a comment associated with the
recipient in question.

Return of Content
Supported where SMTP and NOTARY are used. In principle, principle for |
other situations, this is N/A, as non-delivery notifications |
are not supported. In practice, most RFC 822 systems will
return part or all of the content along with the IP Message
indicating an error (see Non-delivery Notification).

Sensitivity Indication
Supported as new RFC 822 header (Sensitivity:).

Special Delivery
N/A (PDAU).

Stored Message Deletion
N/A (MS).

Stored Message Fetching
N/A (MS).

Stored Message Listing
N/A (MS).

Stored Message Summary
N/A (MS).

Subject Indication
Supported.

Undeliverable Mail with Return of Physical Message
N/A (PDAU).

Use of Distribution List
In principle this applies only to X.400 supported

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Theoretically, this service is N/A (prior). In practice,
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regarded as supported. |

Auto-Submitted Indication |
Supported

2.3.2. Reception by X.400

2.3.2.1. Standard Mandatory Services

The following standard IPM mandatory user facilities are
required for reception of RFC 822 originated mail by an X.400 UA.

Content Type Indication

Delivery Time Stamp Indication

IP Message Identification

Message Identification

Non-delivery Notification

Original Encoded Information Types Indication

Submission Time Stamp Indication

Typed Body

2.3.2.2. Standard Optional Services

The following standard IPM optional user facilities are required
for reception of RFC 822 originated mail by an X.400 UA.

Authorising User's Indication

Blind Copy Recipient Indication

Cross Referencing Indication

Originator Indication

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Replying IP Message Indication

Subject Indication

2.3.2.3. New Services

A new X.400 service "RFC 822 Header Field" is defined using the |
extension facilities. This allows for any RFC 822 header field
to be represented. It may be present in RFC 822 originated
messages, |
messages which are received by an X.400 UA.

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Chapter 3 Basic Mappings

3.1. Notation

The X.400 protocols are encoded in a structured manner according
to ASN.1, whereas RFC 822 is text encoded. To define a detailed
mapping, it is necessary to refer to detailed protocol elements
in each format. A notation to achieve this is described in this
section.

3.1.1. RFC 822

Structured text is defined according to the Extended Backus Naur
Form (EBNF) defined in Section 2 of RFC 822 [21]. [16]. In the EBNF
definitions used in this specification, the syntax rules given in
Appendix D of RFC 822 are assumed. When these EBNF tokens are
referred to outside an EBNF definition, they are identified by
the string "822." appended to the beginning of the string (e.g.,
822.addr-spec). Additional syntax rules, to be used throughout
this specification, are defined in this chapter.

The EBNF is used in two ways.

1. To describe components of RFC 822 messages (or of 822-MTS SMTP |
components). When these new EBNF tokens are referred to *
outside an EBNF definition, they are identified by the
string "EBNF." appended to the beginning of the string
(e.g., EBNF.importance).

2. To describe the structure of IA5 or ASCII information not in
an RFC 822 message. |

For all new EBNF, tokens will either be self delimiting, or be
delimited by self delimiting tokens. Comments and LWSP are not
used as delimiters, except for the following cases, where LWSP
may be inserted according to RFC 822 rules. |

- Around the ":" in all headers

- EBNF.labelled-integer

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- EBNF.object-identifier

- EBNF.encoded-info |

RFC 822 folding rules are applied to all headers. Comments are |
never used in these new headers. |

This notation is used in a modified form to refer to NOTARY |
ENBF [33]. [29]. For this EBNF, the keyword EBNF is it replaces with DSN, |
for example DSN.final-recipient-field fields.

3.1.2. ASN.1

An element is referred to with the following syntax, defined in
EBNF:

element = service "." definition *( "." definition )
service = "IPMS" / "MTS" / "MTA"
definition = identifier / context
identifier = ALPHA *< ALPHA or DIGIT or "-" >
context = "[" 1*DIGIT "]"

The EBNF.service keys are shorthand for the following service
specifications:

IPMS IPMSInformationObjects defined in Annex E of X.420 / ISO
10021-7.

MTS MTSAbstractService defined in Section 9 of X.411 / ISO
10021-4.

MTA MTAAbstractService defined in Section 13 of X.411 / ISO
10021-4. |

FTBP File Transfer Body Part, as defined in [32]. [28]. LP The first
EBNF.identifier identifies a type or value key in the
context of the defined service specification. Subsequent
EBNF.identifiers identify a value label or type in the
context of the first identifier (SET or SEQUENCE).
EBNF.context indicates a context tag, and is used where
there is no label or type to uniquely identify a component.
The special EBNF.identifier keyword "value" is used to
denote an element of a sequence.

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For example, IPMS.Heading.subject defines the subject element of
the IPMS heading. The same syntax is also used to refer to
element values. For example,
MTS.EncodedInformationTypes.[0].g3Fax refers to a value of
MTS.EncodedInformationTypes.[0] .

3.2. ASCII and IA5

A gateway will interpret all IA5 as ASCII. Thus, mapping between
these forms is conceptual.

3.3. Standard Types

There is a need to convert between ASCII text, text and some of the |
types defined in ASN.1 [18]. [14]. For each case, an EBNF syntax
definition is given, for use in all of this specification, which
leads to a mapping between ASN.1, and an EBNF construct. All
EBNF syntax definitions of ASN.1 types are in lower case, whereas
ASN.1 types are referred to with the first letter in upper case.
Except as noted, all mappings are symmetrical.

3.3.1. Boolean

Boolean is encoded as:

boolean = "TRUE" / "FALSE"

3.3.2. NumericString

NumericString is encoded as:

numericstring = *DIGIT

3.3.3. PrintableString

PrintableString is a restricted IA5String defined as:

printablestring = *( ps-char )
ps-restricted-char = 1DIGIT / 1ALPHA / " " / "'" / "+"
/ "," / "-" / "." / "/" / ":" / "=" / "?"
ps-delim = "(" / ")"
ps-char = ps-delim / ps-restricted-char

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This can be used to represent real printable strings in EBNF.

3.3.4. T.61String

In cases where T.61 strings are only used for conveying human
interpreted information, the aim of a mapping is to render the
characters appropriately in the remote character set, rather than
to maximise reversibility. For these cases, there are two |
options, both of which are conformant to this specification: |

1. The mappings to IA5 defined in ITU Recommendation X.408 |
(1988) may be used . [13]. These will then be encoded in
ASCII. | This is the approach mandated in RFC 1327. |

2. This mapping may be used if the characters are not contained |
within ASCII repertoire, but are all in an IANA-registered |
character set. Use the encoding defined in RFC 1522 [14]. [9]. |
to generate appropriate encoded-words. |

Editor's |
T.61 If this mapping is an IANA registered set and could be specified here. |
It has been suggested that ISO 8859-1 should
used, the character set ISO-8859-1 shall be preferred. used if all of |
MIXER could allow options or mandate. Input is solicited.
the characters needed are available in this repertoire. In |
Default approach will
other cases, the character set TELETEX shall be to allow use used. The |
details of any character set. these mappings are defined in the Appendix of |
RFC1494bis.

There is also a need to represent Teletex Strings in ASCII,
for some aspects of O/R Address. For these, the following
encoding is used:

teletex-string = *( ps-char / t61-encoded )
t61-encoded = "{" 1* t61-encoded-char "}"
t61-encoded-char = 3DIGIT

Common characters

Characters in EBNF.ps-char are mapped simply. Other octets, including |
including control characters, are mapped using a quoting
mechanism similar to the printable string mechanism. Each octet
is represented as 3 decimal digits.

There are a number of places where a string may have a Teletex
and/or Printable String representation. The following BNF is
used to represent this.

teletex-and-or-ps = [ printablestring ] [ "*" teletex-string ]

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The natural mapping is restricted to EBNF.ps-char, in order to

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make the full BNF easier to parse.

3.3.5. UTCTime

Both UTCTime and the RFC 822 822.date-time syntax contain: Year
(lowest two digits), Month, Day of Month, hour, minute, second
(optional), and Timezone. 822.date-time also contains an
optional day of the week, but this is redundant. Therefore a
symmetrical mapping can be made between these constructs.

Note:
In practice, a gateway will need to parse various illegal
variants on 822.date-time. In cases where 822.date-time
cannot be parsed, it is recommended that the derived UTCTime
is set to the value at the time of translation.

When mapping to X.400, the UTCTime format which specifies the
timezone offset shall be used.

When mapping to RFC 822, the 822.date-time format shall include a
numeric timezone offset (e.g., +0000).

When mapping time values, the timezone shall be preserved as
specified. The date shall not be normalised to any other
timezone.

3.3.6. Integer

A basic ASN.1 Integer will be mapped onto EBNF.numericstring. In
many cases ASN.1 will enumerate Integer values or use ENUMERATED.
An EBNF encoding labelled-integer is provided. When mapping from
EBNF to ASN.1, only the integer value is mapped, and the
associated text is discarded. When mapping from ASN.1 to EBNF,
addition of an appropriate text label is strongly encouraged.

labelled-integer ::= [ key-string ] "(" numericstring ")"

key-string = *key-char
key-char = <a-z, A-Z, 0-9, and "-">

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3.3.7. Object Identifier

Object identifiers are represented in a form similar to that

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given in ASN.1. The order is the same as for ASN.1 (big-endian).
The numbers are mandatory, and used when mapping from the ASCII
to ASN.1. The key-strings are optional. It is recommended that
as many strings as possible are generated when mapping from ASN.1
to ASCII, to facilitate user recognition.

object-identifier ::= oid-comp object-identifier
| oid-comp

oid-comp ::= [ key-string ] "(" numericstring ")"

An example representation of an object identifier is:

joint-iso-ccitt(2) mhs (6) ipms (1) ep (11) ia5-text (0)

(2) (6) (1)(11)(0)

Because of the use of brackets and the conflict with the RFC 822 |
comment convention, this syntax is not used in structures fields.

3.4. Encoding ASCII in Printable String

Some information in RFC 822 is represented in ASCII, and needs to
be mapped into X.400 elements encoded as printable string. For
this reason, a mechanism to represent ASCII encoded as
PrintableString is needed.

A structured subset of EBNF.printablestring is now defined.
This shall be used to encode ASCII in the PrintableString
character set.

ps-encoded = *( ps-restricted-char / ps-encoded-char )
ps-encoded-char = "(a)" ; (@)
/ "(p)" ; (%)
/ "(b)" ; (!)
/ "(q)" ; (")
/ "(u)" ; (_)
/ "(l)" ; "("
/ "(r)" ; ")"
/ "(" 3DIGIT ")"

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The 822.3DIGIT in EBNF.ps-encoded-char must have range 0-127, and

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is interpreted in decimal as the corresponding ASCII character.
Special encodings are given for: at sign (@), percent (%),
exclamation mark/bang (!), double quote ("), underscore (_), left
bracket ((), and right bracket ()). These characters, with the
exception of round brackets, are not included in PrintableString,
but are common in RFC 822 addresses. The abbreviations will ease
specification of RFC 822 addresses from an X.400 system. These
special encodings shall be interpreted in a case insensitive
manner, but always generated in lower case.

A reversible mapping between PrintableString and ASCII can
now be defined. The reversibility means that some values of
printable string (containing round braces) cannot be generated
from ASCII. Therefore, this mapping must only be used in cases
where the printable strings may only be derived from ASCII (and
will therefore have a restricted domain). For example, in this
specification, it is only applied to a Domain Defined Attribute
which will have been generated by use of this specification and a
value such as "(" would not be possible.

To encode ASCII as PrintableString, the EBNF.ps-encoded
syntax is used, with all EBNF.ps-restricted-char mapped directly.
All other 822.CHAR are encoded as EBNF.ps-encoded-char.

To encode PrintableString as ASCII, parse PrintableString as
EBNF.ps-encoded, and then reverse the previous mapping. If the
PrintableString cannot be parsed, then the mapping is being
applied in to an inappropriate value, and an error shall be given
to the procedure doing the mapping. In some cases, it may be
preferable to pass the printable string through unaltered.

Some examples are now given. Note the arrows which indicate
asymmetrical mappings:

PrintableString ASCII

'a demo.' <-> 'a demo.'
foo(a)bar <-> foo@bar
(q)(u)(p)(q) <-> "_%"
(a) <-> @
(A) -> @
(l)a(r) <-> (a)
(126) <-> ~
( -> (

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( -> ( 2.2

(l) <-> (

3.5. RFC 1522 |

RFC 1522 defines a mechanism for encoding other character set |
information into elements of RFC 822 Headers. A gateway may |
ignore this encoding and treat the elements as ASCII. |

A preferred approach is for the gateway to interpret the RFC |
1522 encoding. This will not always be straightforward, because: |

1. RFC 1522 permits an openly extensible character set choice, |
which may be broader than T.61. |

2. It may not be possible to map all characters into the |
equivalent X.400 field. |

RFC 1522 is only applied to fields which are "for information |
only". A gateway which interprets header elements according to |
RFC 1522 may apply reasonable heuristics to minimise information |
loss.

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Chapter 4 - Addressing and Message IDs |

Addressing is the most complex aspect of X.400 <-> RFC 822 |
gateway and is therefore given a separate chapter. This chapter |
also discusses message identifiers, as they are closely linked to |
addresses. This chapter, as a side effect, also defines a
textual representation of an X.400 O/R Address. This |
specification has much similarity to the X.400(92) representation |
of addresses. This was because early versions of this |
specification were a major input to this work. This |
specification retains compatibility with earlier versions. There The |
is optional compatibility with
the X.400 specification. specification of address representation can be parsed |
but is not generated.

Initially we consider an address in the (human) mail user
sense of "what is typed at the mailsystem to reference a mail
user". A basic RFC 822 address is defined by the EBNF
EBNF.822-address:

822-address = [ route ] addr-spec

In an SMTP (or another 822-MTS protocol, protocol), the originator and each |
recipient are considered to be defined by such a construct. In
an RFC 822 header, the EBNF.822-address is encapsulated in the
822.address syntax rule, and there may also be associated
comments. None of this extra information has any semantics,
other than to the end user.

The basic X.400 O/R Address, used by the MTS for routing, is
defined by MTS.ORAddress. In IPMS, the MTS.ORAddress is
encapsulated within IPMS.ORDescriptor.

It can be seen that RFC 822 822.address must be mapped with
IPMS.ORDescriptor, and that RFC 822 EBNF.822-address must be
mapped with MTS.ORAddress. |

Section 4.1 defines a textual representation of an O/R |
Address, which is used throughout the rest of this specification. |
This text representation is designed to represent an X.400 |
address in the LHS (local part) of an RFC 822 address, and so |
this representation gives a mechanism to represent X.400 |
addresses withing within RFC 822 addresses. |

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Section 4.2 describes a global equivalence mapping between |

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parts of the X.400 and RFC 822 name spaces, which gateways |
conforming to this specification must support. |

Section 4.3 is the core part of this chapter, and defines |
the mapping mechanism.

4.1. A textual representation of MTS.ORAddress

MTS.ORAddress is structured as a set of attribute value pairs.
It is clearly necessary to be able to encode this in ASCII for
gatewaying purposes. All components shall be encoded, in order
to guarantee return of error messages, and to optimise third
party replies. |

4.1.1. Basic O/R Address Representation

An O/R Address has a number of structured and unstructured
attributes. For each unstructured attribute, a key and an
encoding is specified. For structured attributes, the X.400
attribute is mapped onto one or more attribute value pairs. For
domain defined attributes, each element of the sequence will be
mapped onto a triple (key and two values), with each value having
the same encoding. The attributes are as follows, with 1984
attributes given in the first part of the table. For each
attribute, a reference is given, consisting of the relevant
sections in X.402 / ISO 10021-2, and the extension identifier for
88 only attributes:

Attribute (Component) Key Enc Ref Id

84/88 Attributes

MTS.CountryName C P 18.3.3
MTS.AdministrationDomainName ADMD P 18.3.1
MTS.PrivateDomainName PRMD P 18.3.21
MTS.NetworkAddress X121 N 18.3.7
MTS.TerminalIdentifier T-ID P 18.3.23
MTS.OrganizationName O P/T 18.3.9
MTS.OrganizationalUnitNames.value OU P/T 18.3.10
MTS.NumericUserIdentifier UA-ID N 18.3.8
MTS.PersonalName PN P/T 18.3.12
MTS.PersonalName.surname S P/T 18.3.12
MTS.PersonalName.given-name G P/T 18.3.12

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MTS.PersonalName.given-name G P/T 18.3.12
MTS.PersonalName.initials I P/T 18.3.12
MTS.PersonalName
.generation-qualifier GQ P/T 18.3.12
MTS.DomainDefinedAttribute.value DD P/T 18.1

88 Attributes

MTS.CommonName CN P/T 18.3.2 1
MTS.TeletexCommonName CN P/T 18.3.2 2
MTS.TeletexOrganizationName O P/T 18.3.9 3
MTS.TeletexPersonalName PN P/T 18.3.12 4
MTS.TeletexPersonalName.surname S P/T 18.3.12 4
MTS.TeletexPersonalName.given-name G P/T 18.3.12 4
MTS.TeletexPersonalName.initials I P/T 18.3.12 4
MTS.TeletexPersonalName
.generation-qualifier GQ P/T 18.3.12 4
MTS.TeletexOrganizationalUnitNames
.value OU P/T 18.3.10 5
MTS.TeletexDomainDefinedAttribute
.value DD P/T 18.1 6
MTS.PDSName PD-SERVICE P 18.3.11 7
MTS.PhysicalDeliveryCountryName PD-C P 18.3.13 8
MTS.PostalCode PD-CODE P 18.3.19 9
MTS.PhysicalDeliveryOfficeName PD-OFFICE P/T 18.3.14 10
MTS.PhysicalDeliveryOfficeNumber PD-OFFICE-NUM P/T 18.3.15 11
MTS.ExtensionORAddressComponents PD-EXT-ADDRESS P/T 18.3.4 12
MTS.PhysicalDeliveryPersonName PD-PN P/T 18.3.17 13
MTS.PhysicalDeliveryOrganizationName PD-O P/T 18.3.16 14
MTS.ExtensionPhysicalDelivery
AddressComponents PD-EXT-DELIVERY P/T 18.3.5 15
MTS.UnformattedPostalAddress PD-ADDRESS P/T UPA 18.3.25 16 16|
MTS.StreetAddress PD-STREET P/T 18.3.22 17
MTS.PostOfficeBoxAddress PD-BOX P/T 18.3.18 18
MTS.PosteRestanteAddress PD-RESTANTE P/T 18.3.20 19
MTS.UniquePostalName PD-UNIQUE P/T 18.3.26 20
MTS.LocalPostalAttributes PD-LOCAL P/T 18.3.6 21
MTS.ExtendedNetworkAddress
.e163-4-address.number NET-NUM N 18.3.7 22
MTS.ExtendedNetworkAddress
.e163-4-address.sub-address NET-SUB N 18.3.7 22
MTS.ExtendedNetworkAddress
.psap-address NET-PSAP X 18.3.7 22
MTS.TerminalType T-TY I 18.3.24 23

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The following keys identify different EBNF encodings, which are
associated with the ASCII representation of MTS.ORAddress.

Key Encoding

P printablestring
N numericstring
T teletex-string
P/T teletex-and-or-ps
UPA upa-string |
I labelled-integer
X presentation-address

The BNF for presentation-address is taken from the specification |
RFC 1278 "A String Encoding of Presentation Address" [4]. [24].

In most cases, the EBNF encoding maps directly to the ASN.1
encoding of the attribute. There are a few exceptions. In cases
where an attribute can be encoded as either a PrintableString or
NumericString (Country, ADMD, PRMD), either form is mapped into
the BNF. When generating ASN.1, the NumericString encoding shall |
be used if the string contains digits and only digits.

There are a number of cases where the P/T (teletex-and-or-ps)
representation is used. Where the key maps to a single
attribute, this choice is reflected in the encoding of the
attribute (attributes 10-21). For most of the 1984 attributes
and common name, there is a printablestring and a teletex
variant. This pair of attributes is mapped onto the single
component here. This will give a clean mapping for the common
cases where only one form of the name is used.

X.400 (1992) has introduced as string representation of O/R |
Addresses. This

The Unformatted Postal Address has specified a number of string keywords for slightly more complex |
mapping onto a variant of (teletex-and-or-ps), defined as: |

upa-string = [ printable-upa ] [ "*" teletex-string ]
printable-upa = printablestring *( "|" printablestring )

The optional teletex part is straightforward. There is an |
(optional) sequence of printable strings which are mapped in |
order. For example: |

/PD-ADDRESS=The Dome|The Square|Richmond|England/

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X.400 (1992) has introduced as string representation of O/R
Addresses. This has specified a number of string keywords for
attributes. As earlier version versions of this specification were an |
input to this work, many of the keywords are the same. To |
increase compatibility, the following alternative values shall be
recognised when mapping from RFC 822 to X.400. These shall not
be generated when mapping from X.400 to RFC 822.

Keyword Alternative

ADMD A
PRMD P
GQ Q

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When mapping from RFC 822 to X.400, the keywords: OU1, OU2, OU3,
and OU4, shall be recognised. If these are present, no keyword |
OU shall be present. These will be treated as ordered values of |
OU. PD-A1, PD-A2, PD-A3, PD-A4, PD-A5, PD-A6 shall be treated as |
ordered lines. If present, these will be assembled with |
separating line feeds to form a single physical address. In this |
case PD-ADDRESS shall not be present. |

If ISDN is present, is may be interpreted as an E.163/164 |
address, using local heuristics to parse the string. X.400 |
defines the key, but does not give an interpretation of the |
value. |

For T-TY, the X.400 recommended values are preferred, but |
other values are allowed. These values are: tlx; ttx; g3fax; tlx (3); ttx (4); |
g4fax; ia5;

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g3fax (5); g4fax (6); ia5 (7); and vtx. vtx (8).

4.1.2. Encoding of Personal Name

Handling of Personal Name and Teletex Personal Name based purely
on the EBNF.standard-type syntax defined above is likely to be
clumsy. It seems desirable to utilise the "human" conventions
for encoding these components. A syntax is defined, which is
designed to provide a clean encoding for the common cases of O/R
Address specification where:

1. There is no generational qualifier

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2. Initials, if present, contain only letters |

3. Given Name, if present, does not contain full stop ("."), |
and is at least two characters long.

4. Surname does not contain full stop in the first two
characters.

5 If Surname is the only component, it does not contain full
stop.

The following EBNF is defined:

encoded-pn = [ given "." ] *( initial "." ) surname

given = 2*<ps-char not including ".">

initial = ALPHA

surname = printablestring

This is used to map from any string containing only printable
string characters to an O/R address personal name. To map from a
string to O/R Address components, parse the string according to
the EBNF. The given name and surname are assigned directly. All
EBNF.initial tokens are concatenated without intervening full
stops to generate the initials component.

For an O/R address which follows the above restrictions, a
string is derived in the natural manner. In this case, the

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mapping will be reversible.

For example:

GivenName = "Marshall"
Surname = "Rose"

Maps with "Marshall.Rose"

Initials = "MT"
Surname = "Rose"

Maps with "M.T.Rose"

GivenName = "Marshall"
Initials = "MT"
Surname = "Rose"

Maps with "Marshall.M.T.Rose"

Note that X.400 suggest suggests that Initials is used to encode ALL |
initials. Therefore, the defined encoding is "natural" when
either GivenName or Initials, but not both, are present. The |
case where both are present can be encoded, but this appears to
be contrived! encoded.

4.1.3. Standard Encoding of MTS.ORAddress

Given this structure, we can specify a BNF representation of an |
O/R Address.

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EBNF.std-or-address. The more flexible input format is defined |
by EBNF.std-or-address-input. The input BNF has been added |
subsequent to RFC 1327, to reflect the formal incorporation of a |
number of heuristics. The output format is used in all examples.

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standard-type = key-string

registered-dd-type
= key-string dd-key = key-string

value = std-printablestring

std-printablestring
= *( std-char / std-pair ) std-char
= <"{", "}", "*", and any ps-char |
except "/" and "="> "=" >
std-pair = "$" ps-char

The standard-type is any key defined in the table in Section 4.2,
except PN, and DD. The BNF leads to a set of attribute/value
pairs. The value is interpreted according to the EBNF encoding
defined in the table.

If the standard-type is PN, the value is interpreted
according to EBNF.encoded-pn, and the components of
MTS.PersonalName and/or MTS.TeletexPersonalName derived
accordingly.

If dd-key is the recognised Domain Defined string (DD), then
the type and value are interpreted according to the syntax
implied from the encoding, and aligned to either the teletex or
printable string form. Key and value shall have the same
encoding.

If value is "RFC-822", then the (printable string) Domain
Defined Type of "RFC-822" is assumed. This is an optimised
encoding of the domain defined type defined by this
specification.

The matching of all keywords shall be done in a case-
independent manner.

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independent manner.

EBNF.std-or-address uses the characters "/" and "=" as
delimiters. Domain Defined Attributes and any value may contain
these characters. A quoting mechanism, using the non-printable
string "$" is used to allow these characters to be represented.

If the value is registered-dd-type, and the value is
registered at the Internet Assigned Numbers Authority (IANA) as
an accepted Domain Defined Attribute type, then the value shall
be interpreted accordingly. This restriction maximises the
syntax checking which can be done at a gateway.

4.2. |

If an address of this syntax is parsed, and a country value |
is present, but no ADMD, the string shall be interpreted as is an |
ADMD value of single space had been specified.

4.2. Global Address Mapping

From a user perspective, the ideal mapping would be entirely |
symmetrical and global, to enable addresses to be referred to
transparently in the remote system, with the choice of gateway
being left to the Message Transfer Service. There are two
fundamental reasons why this is not possible:

1. The syntaxes are sufficiently different to make this |
impossible. |

2 There is insufficient administrative co-operation between
the X.400 and RFC 822 name registration authorities for this |
to work.

Another way to view this situation is to see that there is not a |
full global equivalence between X.400 and RFC 822 addressing. To |
meet user needs to the extent possible, this specification |
provides for equivalence where there is sufficient co-operation. |
To be useful, this equivalence must be recognised and interpreted |
in the same way by all gateways. Therefore, an asymmetrical
mapping is defined, which can be symmetrical where there is |
appropriate administrative co-operation. Section 4.3 describes |
consider the asymetrical aspects. This section describes how |
the administrative co-ordination for symmetrical mappings is |
achieved. |

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In order to achieve a symmetrical mapping which is supported |
by all gateways which conform to this specification, there is a |
need to define an administrative equivalence between parts of the |
O/R Address and Domain namespaces. This information is defined |
globally, and must be used by any gateway which conforms to this |

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specification. Currently, three ways are defined to access this |
mapping information. |

1. Distribution of text tables. This is described in Appendix |
F of this specification. |

2. Distribution by Domain Name Service. This is described in |
RFC 1664 [9]. | [4].

3. Distribution by X.500 Directory Service. This is defined |
in RFC tbs [31]. | [27].

The following sections define how the namespace equivalence |
is modelled. The Internet Domain Namespace defines a simple |
hierarchy. For the purposes of this mapping, only parts of the |
namespace where domains conform to the EBNF domain-syntax are |
allowed. |

domain-syntax = alphanum [ *alphanumhyphen alphanum ]
alphanum = <ALPHA or DIGIT>
alphanumhyphen = <ALPHA or DIGIT or HYPHEN>

Although RFC 822 allows for a more general syntax, this |
restricted syntax is chosen as it is the one chosen by the |
various domain service administrations. In practice, it reflects |
all RFC 822 usage. |

The following O/R Address attributes are considered as a |
hierarchy, and may be specified by the domain. They are (in |
order of the hierarchy defined by MIXER): |

Country, ADMD, PRMD, Organization, Organizational Unit

There may be multiple Organizational Units. This hierarchy |
reflects most usage of X.400, although X.400 may be used in other |
ways. In particular, it covers the Mnemonic O/R Address using a |
1984 compatible encoding. This is seen as the dominant form of |
O/R Address. MIXER equivalence mappings may only be used when |

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this hierarchy applies. |

An equivalence mapping is defined between two nodes in the |
respective hierarchies. For example: |

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=> "AC.UK" might be mapped with
C="GB", ADMD="GOLD 400", PRMD="UK.AC"

The mapping identifies that the management of these points in the |
respective hierarchies is the same (or co-operate very closely). |
The equivalence means that the namespaces below this equivalence |
point map 1:1, except where the mapping is overridden by further |
equivalence mappings lower down the hierarchy. This equivalence |
may be achieved in three ways: |

1. All of the nodes below this point are RFC 822, and the MIXER |
mapping defines the X.400 addresses for these nodes. |

2. All of the nodes below this point are X.400, and the MIXER |
mapping defines the RFC 822 addresses for these nodes. |

3. There are X.400 and RFC 822 nodes below this point, and |
addressing is managed in a manner which ensures the |
equivalence. The rules to achieve this are defined by |
MIXER. |

A set of global mappings to enable a clean transformation between |
the X.400 and RFC 822 namespaces is therefore defined by |
deployment of MIXER. |

When an equivalence point is defined, a systematic mapping |
for the the inferior nodes in the two hierarchies follows. This |
is a 1:1 the mapping between the nodes in the subtrees. For |
example, given the the equivalence defined above: |

the domain "R-D.Salford.AC.UK" algorithmically maps with
C="GB", ADMD="GOLD 400", PRMD="UK.AC", O="Salford", OU="R-D"

Note that when an equivalence is defined, that this can be re- |
defined for lower points in the hierarchy. However, it is not |
possible to declare contained subtrees to be un-mappable. |

The equivalence mapping also provides a mechanism to deal |

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with missing elements in the X.400 hierarchy (Most (most commonly the |
PRMD). A domain may be associated with an omitted attribute in |
conjunction with several present ones. When performing the |
algorithmic insertion of components lower in the hierarchy, the |

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omitted value shall be skipped. For example: |

If the domain HNE.EGM" is mapped with
"C=TC", "ADMD=ECQ", "PRMD=HNE", and omitted organization

then |

"ZI.HNE.EGM" is algorithmically mapped with
"C=TC", "ADMD=ECQ", "PRMD=HNE", "OU=ZI"

Attributes may have null values, and this is treated separately |
from omitted attributes (while it is not ideal |
to make this distinction, it is useful in practice).

4.2.1. Dynamic Directory and Nameserve Mappings |

When the global mapping is supported by X.500 or DNS, there is |
the possibility that results will be indeterminate due to |
timeout. Lookup should be repeated until a value is determined, |
in order to maintain a correct and consistent global mapping. |

Editor's

Where the mapping relates to addresses in the message |
header, there shall be a timeout in the range of 1-4 hours. If |
This text is
a place-holder, pending discussion. mapping cannot be done in this time, address encapsulation |
shall be used.

4.3. EBNF.822-address <-> MTS.ORAddress |

This section defines the basic address mapping. |

4.3.1. X.400 encoded in RFC 822

This section defines how X.400 addresses are represented in RFC |
822 the addresses. |

The std-or-address syntax is used to encode O/R Address
information in the 822.local-part of EBNF.822-address. Where |
there is an applicable equivalence mapping, further O/R Address
information is associated with the 822.domain component. This
cannot be used in the general case, due to character set

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problems, and to the variants of X.400 O/R Addresses which use
different attribute types. The only way to encode the full
PrintableString character set in a domain is by use of the
822.domain-ref syntax (i.e. 822.atom). This is likely to cause
problems on many systems. The effective character set of domains
is in practice reduced from the RFC 822 set, by restrictions

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imposed by domain conventions and policy, policy [10], and by restrictions the BNF |
definition in
RFC 821. SMTP.

A generic 822.address consists of a 822.local-part and a
sequence of 822.domains (e.g., <@domain1,@domain2:user@domain3>).
All except the 822.domain associated with the 822.local-part
(domain3 in this case) are considered to specify routing within
the RFC 822 world, and will not be interpreted by the gateway
(although they may have identified the gateway from within the
RFC 822 world).

The 822.domain associated with the 822.local-part
identifies the gateway from within the RFC 822 world. This final
822.domain may be used to determine some number of O/R Address
attributes, where this does not conflict with the first role.
RFC 822 routing to gateways will usually be set up to facilitate
the 822.domain being used for both purposes. *

In the case that there is an applicable equivalence mapping, |
the the maximum number of attributes are encoded in the |
822.domain. The remaining attributes are encoded on the LHS,
using the EBNF.std-or-address syntax. For example:

/I=J/S=Linnimouth/GQ=5/@Marketing.Widget.COM

encodes the MTS.ORAddress consisting of:

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MTS.CountryName = "TC"
MTS.AdministrationDomainName = "BTT"
MTS.OrganizationName = "Widget"
MTS.OrganizationalUnitNames.value = "Marketing"
MTS.PersonalName.surname = "Linnimouth"
MTS.PersonalName.initials = "J"
MTS.PersonalName.generation-qualifier = "5"

on the basis of an equivalence between: |

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Domain: Widget.COM
O/R Address: C="TC", ADMD="BTT", O="Widget"

Given the O/R address, the domain Widget.COM is determined from |
the the equivalence mapping and the next component is determined |
algorithmically to give Marketing.Widget.COM. The remaining |
attributes are encoded on the LHS in 822.local-part.

There is a further mechanism to simplify the encoding of *
common cases, where the only attributes to be encoded on the LHS
is a |
are (non-Teletex) Personal Name attributes which comply with the
restrictions of 4.2.1. To achieve this, the 822.local-part shall
be encoded as EBNF.encoded-pn. In the previous example, if the |
GenerationQualifier was not present in the O/R Address, it would
map with the RFC 822 address: J.Linnimouth@Marketing.Widget.COM.

From the standpoint of the RFC 822 Message Transfer System,
the domain specification is used to route the message in the |
standard manner. The standard domain mechanisms are used to
select appropriate gateways for the corresponding O/R Address |
space. It is the responsibility of the management that defines |
the equivalence mapping to define routing in a the manner which |
will enable the message to be delivered.

4.3.2. RFC 822 encoded in X.400

The previous section showed a mapping from X.400 to RFC 822. In |
the case where the mapping was symmetrical and based on the the |
equivalence mapping, this has also shown how RFC 822 is encoded |
in the X.400. This equivalence cannot be used for all RFC 822 |
addresses.

The general case is mapped by use of domain defined

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attributes. A Domain defined type "RFC-822" is defined. The
associated attribute value is an ASCII string encoded according
to Section 3.3.3 of this specification. The interpretation of the |
ASCII string follows RFC 822, and RFC 1123 . [10,16]. Domains
shall | always be fully qualified.

Other O/R Address attributes will be used to identify a
context in which the O/R Address will be interpreted. This might
be a Management Domain, or some part of a Management Domain which
identifies a gateway MTA. For example:

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C = "GB"
ADMD = "GOLD 400"
PRMD = "UK.AC"
O = "UCL"
OU = "CS"
"RFC-822" = "Jimmy(a)WIDGET-LABS.CO.UK"

C = "TC"
ADMD = "Wizz.mail"
PRMD = "42"
"rfc-822" = "postel(a)venera.isi.edu"

Note in each case the PrintableString encoding of "@" as "(a)".
In the second example, the "RFC-822" domain defined attribute is
interpreted everywhere within the (Private) Management Domain.
In the first example, further attributes are needed within the
Management Domain to identify a gateway. Thus, this scheme can
be used with varying levels of Management Domain co-operation.

There is a limit of 128 characters in the length of value of
a domain defined attribute, and an O/R Address can have a
maxmimum of four domain defined attributes. Where the printable
string generated from the RFC 822 address exceeds this value, |
additional domain defined attributes are used to enable up to 512
characters to be encoded. These attributes shall be filled
completely before the next one is started. The DDA keywords
are: RFC822C1; RFC822C2; RFC822C3. Longer addresses cannot be
encoded.

There is, analogous with 4.3.1, a means to associate parts |
of the O/R Address hierarchy with domains. There is an analogous

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global mapping, which in most cases will be the inverse of the
domain to O/R address mapping. The mapping is maintained
separately, as there may be differences (e.g., two alternate
domain names map to the same set of O/R address components).

4.3.3. Component Ordering

In most cases, ordering of O/R Address components is not
significant for the mappings specified. However, Organizational |
Units (printable string and teletex forms) and Domain Defined

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Attributes are specified as SEQUENCE in MTS.ORAddress, and so
their order may be significant. This specification needs to take
account of this:

1. To allow consistent mapping into the domain hierarchy

2. To ensure preservation of order over multiple mappings.

There are three places where an order is specified:

1. The text encoding (std-or-address) of MTS.ORAddress as used
in the local-part of an RFC 822 address. An order is needed
for those components which may have multiple values |
(Organizational Unit, and Domain Defined Attributes). When
generating an 822.std-or-address, components of a given type
shall be in hierarchical order with the most significant
component on the RHS. If there is an Organization |
Attribute, it shall be to the right of any Organizational |
Unit attributes. These requirements are for the following
reasons:

- Alignment to the hierarchy of other components in RFC
822 addresses (thus, Organizational Units will appear |
in the same order, whether encoded on the RHS or LHS).
Note the differences of JNT Mail as described in
Appendix B. |

- Backwards compatibility with RFC 987/1026.

- To ensure that gateways generate consistent addresses.
This is both to help end users, and to generate
identical message ids.

Further, it is recommended that all other attributes are
generated according to this ordering, so that all attributes
so encoded follow a consistent hierarchy. When generating

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822.msg-id, this order shall be followed.

2. For the Organizational Units (OU) in MTS.ORAddress, the |
first OU in the SEQUENCE is the most significant, as
specified in X.400.

3. For the Domain Defined Attributes in MTS.ORAddress, the
First Domain Defined Attribute in the SEQUENCE is the most

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significant.

Note that although this ordering is mandatory for this
mapping, there are NO implications on ordering significance
within X.400, where this is a Management Domain issue.

4.3.4. RFC 822 -> X.400 Basic Address Mapping |

There are two basic cases:

1. X.400 addresses encoded in RFC 822. This will also include
RFC 822 addresses which are given reversible encodings.

2. "Genuine" RFC 822 addresses.

The mapping shall proceed as follows, by first assuming case 1).

STAGE I.

1. If the 822-address is not of the form:

local-part "@" domain

take the domain which will be routed on and apply step 2 of
stage 1 to derive (a possibly null) set of attributes. Then
go to stage II.

NOTE:It may be appropriate to reduce a source route address
to this form by removal of all bar the last domain. In
terms of the design intentions of RFC 822, this would |
be an incorrect action. (Note that a an address of the |
form local%part@domain is not a source route).
However, in most real cases, it will do the "right"
thing and provide a better service to the end user.
This is a reflection on the excessive and inappropriate
use of source routing in | RFC 822 based systems, despite

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the discussion in the | Host Requirements [15]. [10]. Either
approach, or the intermediate approach of stripping
only domain references which reference the local
gateway are conformant to this specification.

2. Attempt to parse EBNF.domain as: |

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*( domain-syntax "." ) known-domain

Where EBNF.known-domain is the longest possible match in the |
set of globally defined mappings described in Section 4.2. |
EBNF.domain-syntax is the restricted domain syntax defined |
in Section 4.2, to which all of the domain components must |
conform for the parse to be successful. If this fails, and
the EBNF.domain does not explicitly identify the local
gateway, go to stage II. If the domain explicitly
identifies the gateway, allocate no attributes. Otherwise | no gateway is explicitly |
identified and all of the | information is used by the local
gateway. In this case | allocate the attributes associated
with EBNF.known-domain. For each component, systematically
allocate the attribute implied by each EBNF.domain-syntax
component in the order: C, ADMD, PRMD, O, OU. Note that if
the mapping used identifies an "omitted attribute", then
this attribute should be omitted in the systematic
allocation. If this new component exceed an upper bound
(ADMD: 16; PRMD: 16; O: 64; OU: 32) or it would lead to
more than four OUs, then go to stage II with the attributes
derived.

At this stage, a set of attributes has been derived, which
will give appropriate routing within X.400. If any of the
later steps of Stage I force use of Stage II, then these
attributes should be used in Stage II. |

3. If the 822.local-part uses the 822.quoted-string encoding,
remove this quoting. If this unquoted 822.local-part has
leading space, trailing space, or two adjacent spaces go to |
stage II.

4. If the unquoted 822.local-part contains any characters not
in PrintableString, go to stage II.

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5. Parse the (unquoted) 822.local-part according to the EBNF
EBNF.std-or-address. Checking of upper bounds should not be
done at this point. If this parse fails, parse the local-
part according to the EBNF EBNF.encoded-pn. If this parse
fails, go to stage II. The result is a set of type/value
pairs. If the set of attributes leads to an address of any
form other than mnemonic form, then only these attributes

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should be taken. If (for mnemonic form) the values generated
conflict with those derived in step 2 (e.g., a duplicated
country attribute), the domain is assumed to be a remote
gateway. In this case, take only the LHS derived
attributes, together with any RHS derived attributes which |
are more significant than the most significant attribute
which is duplicated (e.g., if there is a duplicate PRMD, but
no LHS derived ADMD and country, then the ADMD and country
should be taken from the RHS). Otherwise add LHS and RHS |
derived attributes together.

6. Associate the EBNF.attribute-value syntax (determined from
the identified type) with each value, and check that it
conforms. If not, go to stage II.

7. Ensure that the set of attributes conforms both to the
MTS.ORAddress specification and to the restrictions on this
set given in X.400, and that no upper bounds are exceeded
for any attribute. If not go to stage II.

8. Build the O/R Address from this information.

STAGE II.

This will only be reached if the RFC 822 EBNF.822-address is not
a valid X.400 encoding. This implies that the address must refer
to a recipient on an RFC 822 system. Such addresses shall be
encoded in an X.400 O/R Address using a domain defined attribute.

1. Convert the EBNF.822-address to PrintableString, as
specified in Chapter 3.

2. Generate the "RFC-822" domain defined attribute from this
string.

3. Build the rest of the O/R Address in the manner described

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below.

It may not be possible to encode the domain defined attribute due
to length restrictions. If the limit is exceeded by a mapping at
the MTS level, then the gateway shall reject the message in
question. If this occurs at the IPMS level, then the action will
depend on the policy being taken for IPMS encoding, which is

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discussed in Section 5.1.3.

If Stage I has identified a set of attributes, use these to build
the remainder of the address. The administrative equivalence of
the mappings will ensure correct routing through X.400 to a |
gateway back to RFC 822.

If Stage I has not identified a set of attributes, the
remainder of the O/R address effectively identifies a source
route to a gateway from the X.400 side. There are three cases,
which are handled differently:

822-MTS |

SMTP Return Address |
This shall be set up so that errors are returned through the
same gateway. Therefore, the O/R Address of the local
gateway shall be used.

IPMS Addresses
These are optimised for replying. In general, the message
may end up anywhere within the X.400 world, and so this
optimisation identifies a gateway appropriate for the RFC
822 address being converted. The 822.domain to which the
address would be routed is used to select an appropriate
gateway. A globally defined set of mappings is used, which
identifies (the O/R Address components of) appropriate
gateways for parts of the domain namespace. The longest |
possible match on the 822.domain defines which gateway to |
use, according to the equivalence mappings defined in |
Section 4.2.

This global mapping is used for parts of the RFC 822
namespace which do not have an administrative equivalence
with any part of the X.400 namespace, but for which it is
desirable to identify a preferred X.400 gateway in order to
optimise routing.

If no mapping is found for the 822.domain, a default value

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(typically that of the local gateway) is used. It is never
appropriate to ignore the globally defined mappings. In
some cases, it may be appropriate to locally override the
globally defined mappings (e.g., to identify a gateway close
to a recipient of the message). This is likely to be where
the global mapping identifies a public gateway, and the
local gateway has an agreement with a private gateway which

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it prefers to use.

822-MTS |

SMTP Recipient |
As the RFC 822 and X.400 worlds are in principle fully |
connected, there should be no technical reason for this |
situation to occur. In practice, this is not the case. | In |
some cases, routing may be configured to use X.400 to |
connect two
parts of the an RFC 822 world using X.400. island to the Internet. The information
that this part of the domain space should be routed by X.400
rather than remaining within the RFC 822 world will be
configured privately into the gateway in question. The O/R
address shall then be generated in the same manner as for an
IPMS address, using the globally defined mappings. It is to
support this case that the definition of the global domain
to gateway mapping is important, as the use of this mapping
will lead to a remote X.400 address, which can be routed by
X.400 routing procedures. The information in this mapping
shall not be used as a basis for deciding to convert a
message from RFC 822 to X.400. |

Two examples are given: |

Example 1: (Address not in "localpart" "@" "domainpart") |

@relay.co.uk:userb@host2
maps to
c=gb; a= ; p=uk.ac; o=mhs-relay; dd.rfc-822=(a)relay.co.uk:userb(a)host2;

Example 2: (Address with non printablestring characters) |

Tom_Harris@cs.widget.com
maps to
c=us; a=MCI; P=relay; dd.rfc-822=Tom(u)Harris(a)cs.widget.com;

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4.3.4.1. Heuristics for mapping RFC 822 to X.400

RFC 822 users will often use an LHS encoded address to identify
an X.400 recipient. Because the syntax is fairly complex, a
number of heuristics may be applied to facilitate this form of
usage. A gateway should take care not to be overly "clever" with
heuristics, as this may cause more confusion than a more
mechanical approach.

The heuristics are as follows:

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1. Ignore the omission of a trailing "/" in the std-or syntax.

2. If there is no ADMD component, and both country and PRMD are
present, the value of /ADMD= / (single space) is assumed.

3. Parse the unquoted local part according to the EBNF colon-
or-address. This facilitate users used following heuristic, which relates to this delimiter, |
and also allows the standard string representation ordering of X.400 address |
addresses to
components, may be used (in conjunction with alternate |
attribute keys).

colon-or-address = 1*(attribute "=" value ";" *(LWSP-char))

4. Allow the separator following "DD" or "DDA" to be ":" |
instead of ".", to align with the standard string |
representation of X.400 addresses. |

5. Ignore the omission of a leading "/" in the std-or syntax. |
This is to facilitate a workaround for (non-conformant) |
systems which cannot support when mapping from RFC 822 addresses with a |
leading "/".

The remaining heuristic relates to ordering of address
components. X.400. The
ordering of attributes may be inverted or mixed. For this
reason, the following heuristics may be applied: |

6. If there is an Organization attribute to the left of any Org |
Unit attribute, assume that the hierarchy is inverted. This |
is to facilitate the situation where a user has input the |
attributes in reverse hierarchical order. To do this the |
gateway shall first map according to the order defined in |
4.3.3. If this mapping generates an address which X.400 |
address verification shows to be invalid, this heuristic may |
be applied as an alternative to immediate rejection of the |
address.

4.3.5. X.400 -> RFC 822 Basic Address Mapping |

There are two basic cases:

1. RFC 822 addresses encoded in X.400.

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2. "Genuine" X.400 addresses. This may include symmetrically
encoded RFC 822 addresses.

When a MTS Recipient O/R Address is interpreted, gatewaying will
be selected if there is a single "RFC-822" domain defined |
attribute present and the local gateway is identified by the
remainder of the O/R Address. present. In this case, use mapping A. For
other O/R Addresses which

1. Contain the special attribute.

AND

2. Identifies the local gateway or any other known gateway with
the other attributes.

use mapping A. In A and in other |
cases, use mapping B.

NOTE:
A pragmatic approach would be to assume that any O/R
Address with the special domain defined attribute identifies
an RFC 822 address. This will usually work correctly, but is
in principle not correct. Use of this approach is
conformant to this specification. |

Editor's |
It has been suggested

RFC 1327 specified that this pragmatic approach should only be done when the |
required (HTA),
gateway identfied is local or otherwise known, and identified the |
approach specified here as it usually works. It a pragmatic option. Experience has been suggested |
shown that this approach should not be allowed (AWY), as it causes is effective in practice, despite theoretical |
severe problems
problems. |

If a gateway wishes to make a mapping in some cases. An alternate approach is a manner similar to |
define an alternate value
RFC 1327, but does not wish for which this assumption shall global interpretation (e.g., |
to support an RFC 822 local systems, which does not use global |
addressing), then it should choose a private domain defined |
attribute, different to "RFC-822". An RFC 1327 gateway might be made. |
configurable to operate in this manner.

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Mapping A *

1. Map the domain defined attribute value to ASCII, as defined
in Chapter 3, and drop all other attributes. |

Mapping B.

This is used for X.400 addresses which do not use the explicit
RFC 822 encoding.

1. For all string encoded attributes, remove any leading or

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trailing spaces, and replace adjacent spaces with a single
space.

The only attribute which is permitted to have zero length is
the ADMD. This should be mapped onto a single space.

These transformations are for lookup only. If an |
EBNF.std-or-address mapping is used as in 4), then the |
original values should be used.

2. Map numeric country codes to the two letter values. values (as |
defined in ISO 3166).

3. Noting the hierarchy specified in 4.3.1 and including
omitted attributes, determine the maximum set of attributes
which have an associated domain specification in the
globally defined mapping. If no match is found, allocate |
the domain as the domain specification of the local gateway, described below, and go to step 5.

Note: It might be appropriate The default |
domain to be used is the specification of the local gateway. |
A gateway may use other domains according to private mapping |
tables or heuristics. For example, it may choose a non-local domain.
This would be selected by domain |
which it knows to provide a global mapping analogous free gateway service to | the one described at the end of 4.3.4. This is not |
done.
mapped address.

In cases where the address refers to an X.400 UA, it is
important that the generated domain will correctly route to
a gateway. In general, this is achieved by carefully co-
ordinating RFC 822 routing with the definition of the global
mappings, as there is no easy way for the gateway to make
this check. One rule that shall be used is that domains
with only one component will not route to a gateway. If the
generated domain does not route correctly, the address is
treated as if no match is found.

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4. The mapping identified in 3) gives a domain, and an O/R
address prefix. Follow the hierarchy: C, ADMD, PRMD, O, OU.
For each successive component below the O/R address prefix,
which conforms to the syntax EBNF.domain-syntax (as defined
in 4.3.1), allocate the next subdomain. At least one
attribute of the X.400 address shall not be mapped onto
subdomain, as 822.local-part cannot be null. If there are
omitted attributes in the O/R address prefix, these will
have correctly and uniquely mapped to a domain component.
Where there is an attribute omitted below the prefix, all

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attributes remaining in the O/R address shall be encoded on
the LHS. This is to ensure a reversible mapping. For |
example, if there is an address /S=XX/O=YY/ADMD=A/C=NN/ and |
a mapping for /ADMD=A/C=NN/ is used, then /S=XX/O=YY/ is
encoded on the LHS.

5. If the address contains any attribute not used in mnemonic |
form, then all of the attributes in the address should be
encoded on the LHS in EBNF.std-or-address syntax, as
described below.

For addresses of mnemonic form, if the remaining components
are personal-name components, conforming to the restrictions
of 4.2.1, then EBNF.encoded-pn is derived to form
822.local-part. In other cases the remaining components are
simply encoded as 822.local-part using the
EBNF.std-or-address syntax. If necessary, the
822.quoted-string encoding is used. The following are
examples of legal quoting: "a b".c@x; "a b.c"@x. Either
form may be generated, but the latter is preferred.

If the derived 822.local-part can only be encoded by use of
822.quoted-string, then use of the mapping defined in[24] in[19]
may be appropriate. Use of this mapping is discouraged. |

Editor's Note: |
Can we remove the previous paragraph?

Three examples are given. |

Editor's Note: |
I have had a lot of comments on the inaccuracy of these |
examples. Are they worth retaining? If so, can they be |
carefully verified.

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Example 1: (Address with missing X.400 elements and no specific |
mapping rule for "o=sales; a=Master400; C=it") C=it", where a mapping |

c=it; a=Master400; o=sales;
exsits for master400.it)

C=it; A=Master400; O=sales; S=Support; |
maps to
"/S=Support/o=sales"@Master400.it
/S=Support/o=sales/@Master400.it |

Example 2: (Address with illegal characters in RFC822 generated |
domain if default hierarchical translation (specific mapping rule |
is existing for c=fr; a=atlas; p=autoroutes) is used) |

c=fr; a=atlas; p=autoroutes; o=Region

C=fr; A=atlas; P=autoroutes; O=Region Parisienne; S=rensignments; |
maps to
"/S=rensignments/o=Region Parisienne"@autoroutes.fr Parisienne/"@autoroutes.fr |

Example 3: (Address containing elements not mappable into RFC822 |

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local part) |

c=it; a=PtPostel; DD.cap=20100; DD.ph1=Via

C=it; A=PtPostel; DDA.cap=20100; DDA.ph1=Via Maggiore 11; DD.city=Milano; S=Rossi; DDAs.city=Milano; S=Rossi;|
MAPS TO
"/DD.Cap=20100/DD.ph1=Via Maggiore 11/DD.City=Milano/S=Rossi"@ptpostel.it 11/DD.City=Milano/S=Rossi/"@ptpostel.it|

4.4. Repeated Mappings

There are two types of repeated mapping:

1. A recursive mapping, where the repeat is within one gateway

2 A source route, where the repetition occurs across multiple
gateways

4.4.1. Recursive Mappings

It is possible to supply an address which is recursive at a |
single gateway. For example:

C = "XX"
ADMD = "YY"
O = "ZZ"
"RFC-822" = "Smith(a)ZZ.YY.XX"

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This is mapped first to an RFC 822 address, and then back to the
X.400 address:

C = "XX"
ADMD = "YY"
O = "ZZ"
Surname = "Smith"

In some situations this type of recursion may be frequent. It is
important that where this occurs, that no unnecessary protocol |
conversion occurs. This will minimise loss of service.

4.4.2. Source Routes

The mappings defined are symmetrical and reversible across a
single gateway. The symmetry is particularly useful in cases of
(mail exploder type) distribution list expansion. For example,
an X.400 user sends to a list on an RFC 822 system which he

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belongs to. The received message will have the originator and
any 3rd party X.400 O/R Addresses in correct format (rather than
doubly encoded). In cases (X.400 or RFC 822) where there is
common agreement on gateway identification, then this will apply
to multiple gateways.

When a message traverses multiple gateways, the mapping will
always be reversible, in that a reply can be generated which will
correctly reverse the path. In many cases, the mapping will also
be symmetrical, which will appear clean to the end user. For
example, if countries "AB" and "XY" have RFC 822 networks, but
are interconnected by X.400, the following may happen: The
originator specifies:

Joe.Soap@Widget.PTT.XY

This is routed to a gateway, which generates:

C = "XY"
ADMD = "PTT"
PRMD = "Griddle MHS Providers"
Organization = "Widget Corporation" |
Surname = "Soap"
Given Name = "Joe"

This is then routed to another gateway where the mapping is

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reversed to give:

Joe.Soap@Widget.PTT.XY

Here, use of the gateway is transparent.

Mappings will only be symmetrical where mapping tables equivalences |
are defined. In other cases, the reversibility is more important,
due to the (far too frequent) cases where RFC 822 and X.400
services are partitioned.

The syntax may be used to source route. THIS IS STRONGLY
DISCOURAGED. For example:

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X.400 -> RFC 822 -> X.400

C = "UK"
ADMD = "Gold 400"
PRMD = "UK.AC"
"RFC-822" = "/PN=Duval/DD.Title=Manager/(a)Inria.ATLAS.FR"

This will be sent to an arbitrary UK Academic Community gateway
by X.400. Then it will be sent by JNT Mail to another gateway
determined by the domain Inria.ATLAS.FR (FR.ATLAS.Inria). This
will then derive the X.400 O/R Address:

C = "FR"
ADMD = "ATLAS"
PRMD = "Inria"
PN.S = "Duval"
"Title" = "Manager"

Similarly:
RFC 822 -> X.400 -> RFC 822

"/RFC-822=jj(a)seismo.css.gov/PRMD=AC/ADMD=BT/C=GB/"@monet.berkeley.edu|

"/RFC-822=jj(a)seismo.css.gov/PRMD=AC/ADMD=BT/C=GB/"@monet.berkeley.edu

This will be sent to monet.berkeley.edu by RFC 822, then to the
AC PRMD by X.400, and then to jj@seismo.css.gov by RFC 822.

4.5. Directory Names

Directory Names are an optional part of O/R Name, along with O/R
Address. The RFC 822 addresses are mapped onto the O/R Address

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component. As there is no functional mapping for the Directory
Name on the RFC 822 side, a textual mapping is used. There is no
requirement for reversibility in terms of the goals of this
specification. There may be some loss of functionality in terms
of third party recipients where only a directory name is given,
but this seems preferable to the significant extra complexity of
adding a full mapping for Directory Names. |

The Directory Name shall be represented within an RFC 822 |
comment. Any reasonable format for representing the directory |
name may be used. It is recommended that the directory string |
format of RFC 1485 is used [29]. [25]. The User Friendly Name form of |
RFC 1484 may also be used [30].

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4.6. MTS Mappings

The basic mappings at the MTS level are:

1) 822-MTS SMTP originator -> |
MTS.PerMessageSubmissionFields.originator-name
MTS.OtherMessageDeliveryFields.originator-name ->
822-MTS
SMTP originator |

2) 822-MTS SMTP recipient -> |
MTS.PerRecipientMessageSubmissionFields
MTS.OtherMessageDeliveryFields.this-recipient-name ->
822-MTS
SMTP recipient

822-MTS |

SMTP recipients and return addresses are encoded as |
EBNF.822-address.

The MTS Originator is always encoded as MTS.OriginatorName,
which maps onto MTS.ORAddressAndOptionalDirectoryName, which in
turn maps onto MTS.ORName.

4.6.1. RFC 822 -> X.400 MTS Mappings |

From the 822-MTS SMTP Originator, use the basic ORAddress mapping, to |
generate MTS.PerMessageSubmissionFields.originator-name
(MTS.ORName), without a DirectoryName.

For recipients, the following settings are made for each
component of MTS.PerRecipientMessageSubmissionFields.

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recipient-name
This is derived from the 822-MTS SMTP recipient by the basic |
ORAddress mapping.

originator-report-request
This is be set according to content return policy, as
discussed in Section 5.2.

explicit-conversion
This optional component is omitted, as this service is not
needed

extensions
The default value (no extensions) is used

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4.6.2. X.400 -> RFC 822 MTS Mappings |

The basic functionality is to generate the 822-MTS SMTP originator and |
recipients. There is information present on the X.400 side,
which cannot be mapped into analogous 822-MTS SMTP services. For this |
reason, new RFC 822 fields are added for the MTS Originator and
Recipients. The information discarded at the 822-MTS SMTP level will be |
present in these fields. In some cases a (positive) delivery
report will be generated.

4.6.2.1. 822-MTS SMTP Mappings |

Use the basic ORAddress mapping, to generate the 822-MTS SMTP originator |
(return address) from
MTS.OtherMessageDeliveryFields.originator-name (MTS.ORName). If
MTS.ORName.directory-name is present, it is discarded. (Note
that it will be presented to the user, as described in 4.6.2.2).

The 822-MTS mapping uses the MTA level information, and maps each |
value of MTA.PerRecipientMessageTransferFields.recipient-name, |
where the responsibility bit is set, onto an SMTP recipient. |

Note:The SMTP recipient is conceptually generated from
MTS.OtherMessageDeliveryFields.this-recipient-name. This is
done by taking
MTS.OtherMessageDeliveryFields.this-recipient-name, and |
generating an 822-MTS SMTP recipient according to the basic |
ORAddress mapping, discarding MTS.ORName.directory-name if
present. However, if this model was followed exactly, there

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would be no possibility to have multiple 822-MTS SMTP recipients on |
a single message. This is unacceptable, and so layering is
violated. The
mapping needs to use the MTA level information, and map each
value of MTA.PerRecipientMessageTransferFields.recipient-name,
where the responsibility bit is set, onto an 822-MTS recipient. *

4.6.2.2. Generation of RFC 822 Headers

Not all per-recipient information can be passed at the 822-MTS SMTP |
level. For this reason, two new RFC 822 headers are created, in
order to carry this information to the RFC 822 recipient. These
fields are "X400-Originator:" and "X400-Recipients:".

The "X400-Originator:" field is set to the same value as the
822-MTS |
SMTP originator. In addition, if
MTS.OtherMessageDeliveryFields.originator-name (MTS.ORName)
contains MTS.ORName.directory-name then this Directory Name shall
be represented in an 822.comment.

Recipient names, taken from each value of

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MTS.OtherMessageDeliveryFields.this-recipient-name and
MTS.OtherMessageDeliveryFields.other-recipient-names are made
available to the RFC 822 user by use of the "X400-Recipients:"
field. By taking the recipients at the MTS level, disclosure of
recipients will be dealt with correctly. However, this conflicts
with a desire to optimise mail transfer. There is no problem
when disclosure of recipients is allowed. Similarly, there is no
problem if there is only one RFC 822 recipient, as the |
"X400-Recipients" field is only given one address.

There is a problem if there are multiple RFC 822 recipients,
and disclosure of recipients is prohibited. Two options are
allowed:

1. Generate one copy of the message for each RFC 822 recipient,
with the "X400-Recipients field correctly set to the
recipient of that copy. This is functionally correct, but
is likely to be more expensive.

2. Discard In this case, |
discard the per-recipient information, and insert a field:

X400-Recipients: non-disclosure:;

This is the recommended option.

A third option of ignoring the disclosure flag is not allowed.

If any MTS.ORName.directory-name is present, it shall be *
represented in an 822.comment.

If
MTS.OtherMessageDeliveryFields.orignally-intended-recipient-name
is present, then there has been redirection, or there has been
distribution list expansion. Distribution list expansion is a
per-message option, and the information associated with this is
represented by the "DL-Expansion-History:" field described in |

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Section 5.3.6. Other information is represented in an
822.comment associated associated with
MTS.OtherMessageDeliveryFields.this-recipient-name, The message
may be delivered to different RFC 822 recipients, and so several
addresses in the "X400-Recipients:" field may have such comments.
The non-commented recipient is the RFC 822 recipient. The EBNF of
the comment is:

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redirect-comment =
[ "Originally To:" ] mailbox "Redirected"
[ "Again" ] "on" date-time
"To:" redirection-reason

redirection-reason =
"Recipient Assigned Alternate Recipient"
/ "Originator Requested Alternate Recipient"
/ "Recipient MD Assigned Alternate Recipient"
/ "Recipient Directory Substitution Alternate Recipient"| Recipient"

It is derived from
MTA.PerRecipientMessageTransferFields.extension.redirection-history.
An example of this is:

X400-Recipients: postmaster@widget.com (Originally To:
sales-manager@sales.widget.com Redirected
on Thu, 30 May 91 14:39:40 +0100 To: Originator Assigned
Alternate Recipient postmaster@sales.widget.com Redirected
Again on Thu, 30 May 91 14:41:20 +0100 To: Recipient MD
Assigned Alternate Recipient)

In addition the following per-recipient services from
MTS.OtherMessageDeliveryFields.extensions are represented in
comments if they are used. None of these services can be
provided on RFC 822 networks, and so in general these will be
informative strings associated with other MTS recipients. In some
cases, string values are defined. For the remainder, the string
value shall be chosen by the implementor. If the parameter has
a default value, then no comment shall be inserted when the
parameter has that default value.

requested-delivery-method

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physical-forwarding-prohibited
"(Physical Forwarding Prohibited)".

physical-forwarding-address-request
"(Physical Forwarding Address Requested)".

physical-delivery-modes

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registered-mail-type

recipient-number-for-advice

physical-rendition-attributes

physical-delivery-report-request
"(Physical Delivery Report Requested)".

proof-of-delivery-request
"(Proof of Delivery Requested)".

4.6.2.3. Delivery Report Generation

If SMTP is used, the behaviour is specified in Appendix A. In |
other cases, if |
MTA.PerRecipientMessageTransferFields.per-recipient-indicators
requires a positive delivery notification, this shall be
generated by the gateway. Supplementary Information shall be set
to indicate that the report is gateway generated. This
information shall include the name of the gateway generating the
report.

4.6.3. Message IDs (MTS)

A mapping from 822.msg-id to MTS.MTSIdentifier is defined. The
reverse mapping is not needed, as MTS.MTSIdentifier is always
mapped onto new RFC 822 fields. The value of
MTS.MTSIdentifier.local-part will facilitate correlation of
gateway errors.

To map from 822.msg-id, apply the standard mapping to
822.msg-id, in order to generate an MTS.ORAddress. The Country,
ADMD, and PRMD components of this are used to generate
MTS.MTSIdentifier.global-domain-identifier.
MTS.MTSIdentifier.local-identifier is set to the 822.msg-id,

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including the braces "<" and ">". If this string is longer than
MTS.ub-local-id-length (32), then it is truncated to this length.

The reverse mapping is not used in this specification. It
would be applicable where MTS.MTSIdentifier.local-identifier is
of syntax 822.msg-id, and it algorithmically identifies
MTS.MTSIdentifier.

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4.7. IPMS Mappings

All RFC 822 addresses are assumed to use the 822.mailbox syntax.
This includes all 822.comments associated with the lexical tokens
of the 822.mailbox. In the IPMS O/R Names are encoded as
MTS.ORName. This is used within the IPMS.ORDescriptor,
IPMS.RecipientSpecifier, and IPMS.IPMIdentifier. An asymmetrical
mapping is defined between these components.

4.7.1. RFC 822 -> X.400

To derive IPMS.ORDescriptor from an RFC 822 address.

1. Take the address, and extract an EBNF.822-address. Any |
source routing shall be removed. This can be derived
trivially from either the 822.addr-spec or 822.route-addr
syntax. This is mapped to MTS.ORName as described above,
and used as IMPS.ORDescriptor.formal-name.

2. A string shall be built consisting of (if present):

- The 822.phrase component if the 822.address is an
822.phrase 822.route-addr construct.

- Any 822.comments, in order, retaining the parentheses.

This string is then encoded into T.61 use using a human oriented |
mapping (as described in Section 3.5). If the string is not |
null, it is assigned to IPMS.ORDescriptor.free-form-name.

3. IPMS.ORDescriptor.telephone-number is omitted.

If IPMS.ORDescriptor is being used in IPMS.RecipientSpecifier,
IPMS.RecipientSpecifier.reply-request and
IPMS.RecipientSpecifier.notification-requests are set to default
values (false and none). |

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If the 822.group construct is present, any included
822.mailbox is encoded as above to generate a separate
IPMS.ORDescriptor. The 822.group is mapped to T.61 (as |
described in Section 3.5), and a IPMS.ORDescriptor with only an
free-form-name component built from it.

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4.7.2. X.400 -> RFC 822

Mapping from IPMS.ORDescriptor to RFC 822 address. In the basic
case, where IPMS.ORDescriptor.formal-name is present, proceed as
follows.

1. Encode IPMS.ORDescriptor.formal-name (MTS.ORName) as
EBNF.822-address.

2a. If IPMS.ORDescriptor.free-form-name is present, convert it
to ASCII or T.61 (Section 3.5), and use this as the |
822.phrase component of 822.mailbox using the 822.phrase
822.route-addr construct.

2b. If IPMS.ORDescriptor.free-form-name is absent. If
EBNF.822-address is parsed as 822.addr-spec use this as the
encoding of 822.mailbox. If EBNF.822-address is parsed as |
822.route 822.addr-spec, then a an 822.phrase taken from
822.local-part is added.

3 If IPMS.ORDescriptor.telephone-number is present, this is
placed in an 822.comment, with the string "Tel ". The
normal international form of number is used. For example:

(Tel +44-181-333-7777) |

4. If IPMS.ORDescriptor.formal-name.directory-name is present,
then a text representation is placed in a trailing
822.comment.

5. If IPMS.RecipientSpecifier.report-request has any non-
default values, then an 822.comment "(Receipt Notification
Requested)", and/or "(Non Receipt Notification Requested)",
and/or "(IPM Return Requested)" may be appended to the |
address. "(Receipt Notification Requested)" may be used to |
infer "(Non Receipt Notification Requested)". The effort of
correlating P1 and P2 information is too great to justify

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the gateway sending Receipt Notifications. |

In RFC 1327, inclusion of these comments was mandatory. |
Experience has shown that the clutter and confusion caused |
to RFC 822 users does not justify the information conveyed. |
Implementors are recommended to not include these comments. |
Unless an application is found where retention of these |

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comments is desirable, they will be dropped from the next |
version.

6. If IPMS.RecipientSpecifier.reply-request is True, an
822.comment "(Reply requested)" is appended to the address.

If IPMS.ORDescriptor.formal-name is absent,
IPMS.ORDescriptor.free-form-name is converted to ASCII, and used
as 822.phrase within the RFC 822 822.group syntax. For example:

Free Form Name ":" ";"

Steps 3-6 are then followed.

4.7.3. IP Message IDs

There is a need to map both ways between 822.msg-id and
IPMS.IPMIdentifier. This allows for X.400 Receipt Notifications,
Replies, and Cross References to reference an RFC 822 Message ID,
which is preferable to a gateway generated ID. A reversible and
symmetrical mapping is defined. This provides fully reversible |
mappings when messages pass multiple times across the X.400/RFC
822 boundary.

An important issue with messages identifiers is mapping to
the exact form, as many systems use these ids as uninterpreted
keys. The use of table driven mappings is not always
symmetrical, particularly in the light of alternative domain
names, and alternative management domains. For this reason, a
purely algorithmic mapping is used. A mapping which is simpler
than that for addresses can be used for two reasons:

- There is no major requirement to make message IDs "natural"

- There is no issue about being able to reply to message IDs.
(For addresses, creating a return path which works is more
important than being symmetrical).

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The mapping works by defining a way in which message IDs
generated on one side of the gateway can be represented on the
other side in a systematic manner. The mapping is defined so
that the possibility of clashes is is low enough to be treated as
impossible.

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4.7.3.1. 822.msg-id represented in X.400

IPMS.IPMIdentifier.user is omitted. The
IPMS.IPMIdentifier.user-relative-identifier is set to a printable
string encoding of the 822.msg-id with the angle braces ("<" and
">") removed. The upper bound on this component is 64. The
options for handling this are discussed in Section 5.1.3.

4.7.3.2. IPMS.IPMIdentifier represented in RFC 822

The 822.domain of 822.msg-id is set to the value "MHS". The |
822.local-part of 822.msg-id is constructed as follows. A string |
is build of syntax EBNF.id-loc from IPMS.IPMIdentifier.

id-loc ::= [ printablestring ] "*" [ std-or-address ] |

EBNF.printablestring is the |
IPMS.IPMIdentifier.user-relative-identifier, and EBNF.std-or- |
address being an encoding of the IPMS.IPMIdentifier.user derived |
according to this specification. 822.local-part is derived from |
EBNF.id-loc, if necessary using the 822.quoted-string encoding.
For example:

<"147*/S=Dietrich/O=Siemens/ADMD=DBP/C=DE/"@MHS>

4.7.3.3. 822.msg-id -> IPMS.IPMIdentifier

If the 822.local-part can be parsed as:

[ printablestring ] "*" [ std-or-address ]

and the 822.domain is "MHS", then this ID was X.400 generated.
If EBNF.printablestring is present, the value is assigned to
IPMS.IPMIdentifier.user-relative-identifier. If
EBNF.std-or-address is present, the O/R Address components
derived from it are used to set IPMS.IPMIdentifier.user.

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Otherwise, this is an RFC 822 generated ID. In this case,
set IPMS.IPMIdentifier.user-relative-identifier to a printable
string encoding of the 822.msg-id without the angle braces.

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4.7.3.4. IPMS.IPMIdentifier -> 822.msg-id

If IPMS.IPMIdentifier.user is absent, and
IPMS.IPMIdentifier.user-relative-identifier mapped to ASCII and
angle braces added parses as 822.msg-id, then this is an RFC 822
generated ID.

Otherwise, the ID is X.400 generated. Use the
IPMS.IPMIdentifier.user to generate an EBNF.std-or-address form
string. Build the 822.local-part of the 822.msg-id with the
syntax:

[ printablestring ] "*" [ std-or-address ]

The printablestring is taken from
IPMS.IPMIdentifier.user-relative-identifier. Use
822.quoted-string if necessary. The 822.msg-id is generated with
this 822.local-part, and "MHS" as the 822.domain.

4.7.3.5. Phrase form

In "InReply-To:" "In-Reply-To:" and "References:", the encoding 822.phrase may |
be used as an alternative to 822.msg-id. To map from 822.phrase
to IPMS.IPMIdentifier, assign
IPMS.IPMIdentifier.user-relative-identifier to the phrase. When
mapping from IPMS.IPMIdentifier for "In-Reply-To:" and
"References:", if IPMS.IPMIdentifier.user is absent and
IPMS.IPMIdentifier.user-relative-identifier does not parse as
822.msg-id, generate an 822.phrase rather than adding the domain
MHS.

4.7.3.6. RFC 987 backwards compatibility

The mapping defined here is different to that used in RFC 987, as
the RFC 987 mapping lead to changed message IDs in many cases.
Fixing the problems is preferable to retaining backwards
compatibility. An implementation of this standard is encouraged
to recognise message IDs generated by RFC 987. This is not
required.

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RFC 987 generated encodings may be recognised as follows.
When mapping from X.400 to RFC 822, if the
IPMS.IPMIdentifier.user-relative-identifier is "RFC-822" the id
is RFC 987 generated. When mapping from RFC 822 to X.400, if the

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822.domain is not "MHS", and the 822.local-part can be parsed as

[ printablestring ] "*" [ std-or-address ]

then it is RFC 987 generated. In each of these cases, it is
recommended to follow the RFC 987 rules.

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Chapter 5 - Detailed Mappings

This chapter specifies detailed mappings for the functions
outlined in Chapters 1 and 2. It makes extensive use of the
notations and mappings defined in Chapters 3 and 4.

5.1. | RFC 822 -> X.400: Detailed Mappings |

The mapping of RFC 822 and MIME messages to X.400 InterPersonal |
Messages is described in Sections 5.1.1 to 5.1.7. Mapping of |
NOTARY format delivery status notifications, which are all |
messages of type multipart/report and subtype |
delivery-status-notifications to X.400 delivery reports is |
covered in Section 5.1.8.

5.1.1. Basic Approach

A single IP Message is generated from an RFC 822 message message. The |
RFC 822 headers are used to generate the IPMS.Heading. *

Some RFC 822 fields cannot be mapped onto a standard IPM
Heading field, and so an extended field is defined in Section
5.1.2. This is then used for fields which cannot be mapped onto
existing services.

The message is submitted to the MTS, and the services
required can be defined by specifying
MTS.MessageSubmissionEnvelope. A few parameters of the MTA
Abstract service are also specified, which are not in principle
available to the MTS User. Use of these services allows RFC 822
MTA level parameters to be carried in the analogous X.400 service
elements. The advantages of this mapping far outweigh the
layering violation.

5.1.2. X.400 Extension Field

An IPMS Extension is defined:

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rfc-822-field HEADING-EXTENSION
VALUE RFC822FieldList
::= id-rfc-822-field-list

RFC822FieldList ::= SEQUENCE OF RFC822Field

RFC822Field ::= IA5String

The Object Identifier id-rfc-822-field-list is defined in
Appendix D.

To encode any RFC 822 Header using this extension, an
RFC822Field element is built using the 822.field omitting the
trailing CRLF (e.g., "Fruit-Of-The-Day: Kiwi Fruit"). All fields |
shall be unfolded. There shall be no space before the ":". The
reverse mapping builds the RFC 822 field in a straightforward
manner. This RFC822Field is appended to the RFC822FieldList,
which is added to the IPM Heading as an extension field.

5.1.3. Generating the IPM

The IPM (IPMS Service Request) is generated according to the
rules of this section. The IPMS.IPM.body is generated from the |
RFC 822 message body in the manner described in Section 5.1.5.

If no specific 1988 features are used, the IPM generated is
encoded as content type 2. Otherwise, it is encoded as content
type 22. The latter will always be the case if extension heading
fields are generated.

When generating the IPM, the issue of upper bounds are |
handled as follows. This approach removes a choice of options |
given in RFC 1327, based on operational experience. Truncate | fields to the upper bounds specified
in X.400. This will prevent | problems with UAs which enforce
upper bounds, but will sometimes | discard useful information.
This approach will cause more | problems for some fields than
others (e.g., truncating an O/R | Address component that would be
used to route a reply would be a | more severe problem than
truncating a Free Form Name). If the | Free Form name is
truncated, it shall be done so that it does not | break RFC 822 comments. |
comments and RFC 1522 encoding. |

Note:This approach removes a choice of options given in RFC 1327, |

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based on operational experience.

The rest of this section concerns IPMS.IPM.heading
(IPMS.Heading). The only mandatory component of IPMS.Heading is
the IPMS.Heading.this-IPM (IPMS.IPMIdentifier). A default is
generated by the gateway. With the exception of "Received:", the
values of multiple fields are merged (e.g., If there are two
"To:" fields, then the mailboxes of both are merged to generate a
single list which is used in the IPMS.Heading.primary-recipients.
Information shall be generated from the standard RFC 822 Headers
as follows:

Date:
Ignore (Handled at MTS level)

Received:
Ignore (Handled at MTA level)

Message-Id:
Mapped to IPMS.Heading.this-IPM. For these, and all other
fields containing 822.msg-id the mappings of Chapter 4 are
used for each 822.msg-id.

From:
If Sender: is present, this is mapped to
IPMS.Heading.authorizing-users. If not, it is mapped to
IPMS.Heading.originator. For this, and other components
containing addresses, the mappings of Chapter 4 are used for
each address.

Sender:
Mapped to IPMS.Heading.originator.

Reply-To:
Mapped to IPMS.Heading.reply-recipients.

To: Mapped to IPMS.Heading.primary-recipients

Cc: Mapped to IPMS.Heading.copy-recipients.

Bcc: Mapped to IPMS.Heading.blind-copy-recipients if there is at
least one BCC: recipient. If there are no recipients in
this field, it should be mapped to a zero length sequence.

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In-Reply-To:
If there is one value, it is mapped to

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IPMS.Heading.replied-to-IPM, using the 822.phrase or
822.msg-id mapping as appropriate. If there are several
values, they are mapped to IPMS.Heading.related-IPMs, along
with any values from a "References:" field.

References:
Mapped to IPMS.Heading.related-IPMs.

Keywords:
Mapped onto a heading extension.

Subject:
Mapped to IPMS.Heading.subject. The field-body uses the |
human oriented mapping referenced in Section 3.3.4.

Comments:
Mapped onto a heading extension. This is a change from |
1327, which specified to generate an IPMS.BodyPart of type
IPMS.IA5TextBodyPart with
IPMS.IA5TextBodyPart.parameters.repertoire set to the
default (ia5), containing the value of the fields, preceded
by the string "Comments: " and that this body part shall |
precede the other one. Experience has shown that this |
complexity is not justified. This text is retained to |
facilitate backwards compatibility.

Encrypted:
Mapped onto a heading extension.

Resent-*
Mapped onto a heading extension.

Note that it would be possible to use a ForwardedIPMessage
for these fields, but the semantics are (arguably) slightly
different, and it is probably not worth the effort. |

Content-Language: |
This fields is defined in RFC 1766 [13]. [8]. Map this onto the first two |
IPM language extension. RFC 1766 allows for more |
information than can be mapped
characters of each value given onto the IPM Languages |
extension. If any comments or values longer than two |
information is lost in the mapping,
characters occur, a header extension shall | also be |
generated.

Other Fields

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Other Fields
In particular X-* fields, and "illegal" fields in common
usage (e.g., "Fruit-of-the-day:") are mapped onto a heading
extension, unless covered by another section or appendix of
this specification. The same treatment is applied to RFC
822 fields where the content of the field does not conform
to RFC 822 (e.g., a Date: field with unparseable syntax). |

The MIME heading are mapped as follows. They will only be |
present for messages and not for other MIME content types. When | performing a reverse |
mapping from X.400 to MIME, these fields may | be treated as a hint
to help convert the message as well as | possible. Only one value
for each field shall be present in the | MIME message that is thus
generated. |

MIME-Version: |
Mapped onto a heading extension. |

Content-Transfer-Encoding: |
Mapped onto a heading extension. |

Content-Type |
Mapped onto a heading extension. |

Content-ID |
Mapped onto a heading extension. |

Content-Description |
Mapped onto a heading extension.

5.1.4. Generating the IPM Body |

If the header does not contain a 822.MIME-Version field, then |
generate a IPMS.Body with a single IPMS.BodyPart of type |
IPMS.IA5TextBodyPart with |
IPMS.IA5TextBodyPart.parameters.repertoire set to the default |
(ia5) containing the body of the RFC 822 message. |

If 822.MIME-Version is present, then the body part is |
analysed as a MIME message and the elements treated as described |
below. |

5.1.4.1. Mapping Multiparts |

A MIME multipart is a set of content-types and not a message with |

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a set of content types. When the multipart is at the outermost |
MIME header and is either multipart/digest or multipart/mixed, |
elements of the multipart are mapped directly onto IPMS.BodyPart. |
In other cases, a MIME multipart is mapped to an |
IPMS.MessageBodyPart containing an IPMS.BodyPart for each element |
of the multipart. |

When a nested IPMS.Message is generated from a multipart, an |
IPMS.heading shall always be generated. The only mandatory field |
is the IPMS.Heading.this-IPM message id, which shall be generated |
by the gateway. An IPMS.Heading.subject field shall also be |
generated, in order to provide useful information to non-MIME |
capable X.400(88) UAs and to all X.400(84) UAs. The subject |
field is set as follows according to the multipart subtype: |

mixed: "Multipart Message"
alternative: "Alternative Body Parts containing the same information"
digest: "Message Digest"
parallel: "Body Parts interpreted in parallel"
other: "Multipart Message (<subtype>)"

For other types of multipart, the multipart subtype shall be |
included in the subject line. |

For each multipart, the following IPMS.HeadingExtension shall be |
generated, with the enumerated value set according to the |
subtype: |

multipart-message HEADING-EXTENSION
VALUE MultipartType
::= id-hex-multipart-message

MultipartType ::= IA5String

The MultipartType contains the subtype, for example "digest". If |
this heading is present when mapping from X.400 to MIME, the the |
appropriate multipart may be generated. |

5.1.4.2. Mapping Content Type Message |

When a message subtype is contained within a MIME message, it is |
mapped to an IPMS.MessageBodyPart according to this |
specification. Any mappings that would have been made to the MTS |
Abstract Service are placed in |

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IPMS.MessageBodyPart.parameters.delivery-envelope. |

Content type message has three subtypes, which are handled |
as follows: |

message/rfc822 |
Mapped onto IPMS.ForwardedIPMessage. |

message/external |
This points to an external body part. As this will not in |
general be accessible to the X.400 recipient, the body part |
shall be resolved at the gateway. gateway, unless it is already |
included in a multipart/alternative or the recipient UA is |
known to be capable of handling a message/external tunnelled |
body part. The gateway shall obtain | the body part and then |
map it as if it had been included. | If the expiration date
of the external body part has | expired, the gateway may |
tunnel the body part as described part. |

Editor's Note: |
There has been comment that this dereference should be made |
more optional or the text changed in RFC 1494. some way. Input is |
solicited.

message/partial |
The following heading extension is added, derived from the |
message/partial parameters, in order to facilitate MIME |
capable X.400 UAs to handle messages of this type: |

partial-message HEADING-EXTENSION
VALUE PartialMessage
::= id-hex-partial-message

PartialMessage ::=
SEQUENCE {
number INTEGER,
total INTEGER,
id IA5String
}

message/other |
No specific treatment is defined for other subtypes of |
message. Treatment for new message subtypes may be defined |

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in future versions of MIXER. |

5.1.4.3. Mapping Other Content Types |

All other MIME content types are atomic data, and can be regarded |
as message attachments. |

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The following basic types and some subtypes are defined in |
MIME: text; application; image; audio; video. The mapping to |
X.400 of the types defined in MIME is specified in RFC 1494bis. |

5.1.4.4. Mapping to Body Part 15 |

RFC 1494bis defines mappings onto Body Part 15. Similar |
considerations apply to body parts 1-14. MIME defines two | fields |
which add information to MIME contents. These Two of these are |
"Content-ID", and "Content-Description". When mapping to body |
part 15, this information must be discarded, unless the specific |
body part 15 mapping allows it to be retained. |

5.1.4.5. Mapping to the EMA FTBP |

EMA has defined a profile for use of the File Transfer Body Part |
(FTBP) . [32] [28] MIXER considers spepcifies mapping to FTBP, as defined by |
this profile. MIXER does not define when this mapping is to be |
used. This is a matter for gateway configuration and the user |
agent capabilities.

The exact mapping will depend on the attachment being |
mapped, and so cannot be defined here. The MIME headers are |
mapped as follows: |

Content-ID: |
If this is present, create an element |
FTBP.FileTransferParameters.related-stored-file. file- |
identifier.cross-refernce.message-reference |
file-identifier.cross-refernce.message-reference
FTBP.FileTransferParameters.related-stored-file. file- |
identifier.cross-refernce.message-reference
file-identifier.cross-refernce.message-reference and set it
to | the IPM.MessageIdentifier derived from the "Content-ID:". |
FTBP.FileTransferParameters.related-stored-file. "Content-ID:".
FTBP.FileTransferParameters.related-stored-file.
relationship.descriptive-relationship is set to the string
"Internet MIME Body Part".
FTBP.FileTransferParameters.related-stored-file. |
file-identifier.cross-refernce.application-crossreference is

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set to a null OCTET STRING.

Content-Descriptor:
This is mapped to the first string in
FTBP.FileTransferParameters.environment.user-visible-string. |

A specific mapping for multipart/appledouble is defined. Noting |
that the fileTransferData component of an FTBP is a SEQUENCE of |
EXTERNAL, the file data component of the multipart is mapped onto |
the first of two elements of the SEQUENCE, and the |
application/applefile component (the finder and resource info) is |
mapped onto the second element of the sequence. Applications |
which don't care about the finder and resource info can, |
therefore, simply ignore the second element and extract the data |
from the first element. The direct reference component of the |
relationship.descriptive-relationship
first element is set to reflect the original type/subtype of the string |
"Internet
MIME Body Part". |
FTBP.FileTransferParameters.related-stored-file. file- |
identifier.cross-refernce.application-crossreference is set |
to a null OCTET STRING. data component, according the OID's defined in RFC1494bis. |

Content-Descriptor:

Editor's Note: |
This specification is mapped to the first string in |
FTBP.FileTransferParameters.environment.user-visible-string. clearly useful and needed. Does it |
belong in MIXER? Comments solicited.

5.1.4.6. Encapsulation in X.400 |

Where no mapping is possible, the gateway may choose to discard |

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the body part or to reject the message. This will depend on |
gateway policy, and configuration knowledge. Another option is |
to "tunnel" the body part, by encapsulating it in X.400. This |
section defines an extended body part, based on body part 15, |
which may be used to hold any MIME content. |

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mime-body-part EXTENDED-BODY-PART-TYPE
PARAMETERS MimeParameters
IDENTIFIED BY id-mime-body-part-parameters
DATA OCTET STRING
::= id-mime-body-part

MimeParameters ::=
SEQUENCE {
content-type IA5String,
content-parameters SEQUENCE OF
SEQUENCE {
parameter IA5String,
parameter-value IA5String
}
other-header-fields RFC822FieldList
}

The OBJECT IDENTIFIERS id-mime-body-part and id-mime-parameters |
id-mime-body-part-parameters are defined in Appendix D. A MIME
content is mapped onto this | body part. The MIME headers of the
body part are mapped as | follows: |

Content-Type: |
The "type/subtype" string is mapped to |
MimeParameters.content-type. |

OtherTake all other headers and create |
MimeParameters.other-header-fields, by concatenating them |
together. |

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Convert the MIME body part into its canonical form, as specified |
in Appendix H of MIME [14]. [9]. This canonical form is used to |
generate the mime-body-part.data octet string. |

The Parameter mapping may be used independently of the body |
part mapping (e.g., in order to use a different encoding is used | for the a |

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mapped MIME body part). |

This body part contains all of the MIME information, and so |
can be mapped back to MIME without loss of information. |

5.1.5. Mappings to the MTS Abstract Service

The MTS.MessageSubmissionEnvelope comprises
MTS.PerMessageSubmissionFields, and
MTS.PerRecipientMessageSubmissionFields. The mandatory
parameters are defaulted as follows.

MTS.PerMessageSubmissionFields.originator-name
This is always generated from 822-MTS, SMTP, as defined in Chapter 4. |

MTS.PerMessageSubmissionFields.content-type
Set to the value implied by the encoding of the IPM (2 or
22).

MTS.PerRecipientMessageSubmissionFields.recipient-name
These will always be supplied from 822-MTS, SMTP, as defined in |
Chapter 4.

Optional components are omitted, and default components
defaulted. This means that disclosure of recipients is
prohibited and conversion is allowed. There are two exceptions
to the defaulting. For
MTS.PerMessageSubmissionFields.per-message-indicators, the
following settings are made:

- Alternate recipient is allowed, as it seems desirable to
maximise the opportunity for (reliable) delivery.

- Content return request *

If SMTP is set according to the issues
discussed used, Appendix A shall be followed in Section 5.2. setting these |
parameters.

MTS.PerMessageSubmissionFields.original-encoded-information-types

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is a set of one element BuiltInEncodedInformationTypes.ia5-text. derived from the message generated by the gateway, and shall |
reflect all body parts. |

The MTS.PerMessageSubmissionFields.content-correlator is encoded
as IA5String, and contains the Subject:, Message-ID:, Date:, and
To: fields (if present). This includes the strings "Subject:",
"Date:", "To:", "Message-ID:", and appropriate folding. folding to make |

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the field appear readable. This shall be truncated to
MTS.ub-content-correlator-length (512) characters. In addition,
if there is a "Subject:" field, the
MTS.PerMessageSubmissionFields.content-identifier, is set to a
printable string representation of the contents of it. If the
length of this string is greater than MTS.ub-content-id-length
(16), it should be truncated to 13 characters and the string
"..." appended. Both are used, due to the much larger upper bound
of the content correlator, and that the content id is available
in X.400(1984).

5.1.6. Mappings to the MTA Abstract Service

There is a need to map directly onto some aspects of the MTA
Abstract service, for the following reasons:

- So the the MTS Message Identifier can be generated from the
RFC 822 Message-ID:.

- So that the submission date can be generated from the
822.Date.

- To prevent loss of trace information

- To prevent RFC 822/X.400 looping caused by distribution
lists or redirects

The following mappings are defined.

Message-Id:
If this is present, the
MTA.PerMessageTransferFields.message-identifier is generated
from it, using the mappings described in Chapter 4. |

This mapping arguably generates messages which do not |
conform to US GOSIP, GOSIP (1984 version only), which states: |

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6.7.e MPDI Identifier Validation |

(1) Validation of the GlobalDomainIdentifier component of the MPDU MPDU|
Identifier is performed on reception of a message (i.e. the result result|
of a TRANSFER.Indication). |
|
(2) The country name should be known to the validating domain, and and|
depending on the country name, validation of the ADMD name may also also|
be possible. |

(3) Additional validation of the GlobalDomainIdentifier is performed performed|
against the corresponding first entry in the TraceInformation. If If|
inconsistencies are found during the comparison, a non-delivery non-delivery|
notice with the above defined reason and diagnosticcode is |
generated. |

(4) A request will be generated to the CCITT for a more meaningful meaningful|
diagnostic code (such as "InconsistentMPUTIdentifier"). |

This applies to ADMDs only, and is specified in the 1984 |
version and not the 1988 version. Conformance depends on the |
interpretation of "inconsistency". The specification makes |
the most sensible choice, and so is not being changed in the |
update from RFC 1327.

Date:
This is used to set the first component of
MTA.PerMessageTransferFields.trace-information
(MTA.TraceInformationElement). The 822-MTS SMTP originator is |
mapped into an MTS.ORAddress, and used to derive
MTA.TraceInformationElement.global-domain-identifier. The
optional components of
MTA.TraceInformationElement.domain-supplied-information are
omitted, and the mandatory components are set as follows:

MTA.DomainSuppliedInformation.arrival-time
This is set to the date derived from Date:

MTA.DomainSuppliedInformation.routing-action
Set to relayed.

The first element of

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MTA.PerMessageTransferFields.internal-trace-information is
generated in an analogous manner, although this can be
dropped later in certain circumstances (see the procedures

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for "Received:"). The
MTA.InternalTraceInformationElement.mta-name is derived from
the 822.domain in the 822 MTS Originator address.

Received:
All RFC 822 trace is used to derive
MTA.PerMessageTransferFields.trace-information and
MTA.PerMessageTransferFields.internal-trace-information.
Processing of Received: lines follows processing of Date:,
and is be done from the the bottom to the top of the RFC 822
header (i.e., in chronological order). When other trace |
elements (in particular X400-Received:) are processed the |
relative ordering (top to bottom of the header) shall be |
retained correctly. The initial element of
MTA.PerMessageTransferFields.trace-information will be
generated already (from Date:), unless the message has
previously been in X.400, when it will be derived from the
X.400 trace information.

Consider the Received: field in question. If the "by" part
of the received is present, use it to derive an
MTS.GlobalDomainIdentifier. If this is different from the
one in the last element of
MTA.PerMessageTransferFields.trace-information
(MTA.TraceInformationElement.global-domain-identifier)
create a new MTA.TraceInformationElement, and optionally
remove
MTA.PerMessageTransferFields.internal-trace-information.
This removal shall be done in cases where the message is
being transferred to another MD where there is no bilateral
agreement to preserve internal trace beyond the local MD.
The trace creation is as for internal trace described below,
except that no MTA field is needed. |

Editor's Note: |
It has been proposed to remove this paragraph, as this |
should be done by the MTA beyond the gateway. Input |
solicited.

Then add a new element (MTA.InternalTraceInformationElement)
to MTA.PerMessageTransferFields.internal-trace-information,

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creating this if needed. This shall be done, even if
inter-MD trace is created. The
MTA.InternalTraceInformationElement.global-domain-identifier
is set to the value derived. The
MTA.InternalTraceInformationElement.mta-supplied-information
(MTA.MTASuppliedInformation) is set as follows:

MTA.MTASuppliedInformation.arrival-time
Derived from the date of the Received: line

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MTA.MTASuppliedInformation.routing-action
Set to relayed

The MTA.InternalTraceInformationElement.mta-name is taken
from the "by" component of the "Received:" field, truncated
to MTS.ub-mta-name-length (32). For example:

Received: from computer-science.nottingham.ac.uk by
vs6.Cs.Ucl.AC.UK via Janet with NIFTP id aa03794;
28 Mar 89 16:38 GMT

Generates the string

vs6.Cs.Ucl.AC.UK

Note that before transferring the message to some ADMDs,
additional trace stripping may be required, as the implied path
through multiple MDs would violate ADMD policy. This will
depend on bilateral agreement with the ADMD. |

The gateway itself shall not add trace information. |
However, for trace purposes, the gateway shall be considered as |
an X.400 and Internet MTA back to back, and both of these shall |
add trace elements.

5.1.7. Mapping New Fields

This specification defines a number of new fields for Reports,
Notifications and IP Messages in Section 5.3. As this
specification only aims to preserve existing services, a Messages. A gateway conforming to this |
specification does not need to shall map all of these fields to X.400.

Two X.400, except as |
defined below.

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The mapping of two extended fields must be mapped, is particularly |
important, in order to prevent looping. "DL-Expansion-History:"
is mapped to
MTA.PerMessageTransferFields.extensions.dl-expansion-history
X400-Received: must be mapped to
MTA.PerMessageTransferFields.trace-information and
MTA.PerMessageTransferFields.internal-trace-information. In
cases where X400-Received: is present, the usual mapping of Date:
to generate the first element of trace should not be done. This
is because the message has come from X.400, and so the first

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element of trace can be taken from the first X400-Received:.

The following fields shall not be mapped, and shall be |
discarded:

- Discarded-X400-MTS-Extensions:

- Message-Type:

- Discarded-X400-IPMS-Extensions: *

- X400-Content-Type:

- X400-Originator:

- X400-Recipients:

- X400-MTS-Identifier:

Other fields may be either discarded or mapped to X.400. It
is usually desirable and beneficial to do map, particularly to
facilitate support of a message traversing multiple gateways.
These mappings may be onto MTA, MTS, or IPMS services. The level
of support for Mapping this reverse mapping should field would be indicated useful in the |
Gateway conformance statement.
some circumstances, but very dangerouts in others (e.g., |
following an internet list expansion). Therefore it is not |
mapped.

5.1.8. Mapping Delivery Status Notifications to X.400 |

5.1.8.1. Basic Model |

Internet Mail delivery status notifications (DSN) are mapped to |
X.400 delivery reports. With message mapping, information |
without a mapping is carried by and an IPM Extension. This cannot |
be done for delivery reports. Two mechanisms are used for |
information where there is not a direct mapping. |

The first mechanism is to define extensions, which allow all |

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of the DSN information to be carried in the delivery report. |
This is not completely satisfactory for two reasons: |

1. User defined extensions are supported by the ISO version of |
the standard, but not the CCITT one. Therefore, |
implementation support for these extensions will not be |

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universal. |

2 X.400 User Agent implementations will not in general |
recognise these extensions. Therefore, although the |
information will be present, it will often not be available. available |
to the user. This may be very problematic, as this
information may be | critical to diagnosing the reason for a
failure. |

Therefore a second mechanism is defined. This shall always |
be used when the DSN contains non-delivery information, and may |
be used in other cases. This mechanism is to map the whole DSN |
(as if it was were an ordinary multipart) into the return of content. |
This will make the DSN information available as a text body part |
in the outer message, with the real returned content as an |
enclosed message. This mechanism will ensure that information is |
not lost at the gateway. |

5.1.8.2. DSN Extensions |

Two X.400 MTS extensions are defined as follows: |

dsn-header-list EXTENSION
RFC822FieldList
::= id-dsn-header-list

dsn-field-list EXTENSION
RFC822FieldList
::= id-dsn-field-list

The Object Identifiers id-dsn-heade-list id-dsn-header-list and id-dsn-field-list |
are defined in Appendix D. These extension is used in the same |
way as the IPM extension rfc-822-field, described in Section |
5.1.2. IPM extension rfc-822-field, described in Section |
5.1.2. These extensions may only be used with ISO-10021, and |
not X.400 (which does not allow user extensions at the MTS |
level).

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5.1.8.3. DSN to Delivery Report Mapping |

Reports may not be submitted in the X.400 model, and so the |
report submission is considered in terms of the MTA Abstract |
Service. An MTA.Report is constructed. The |
MTA.ReportTransferFields.report-identifier is generated from the |
Message-Id of the DSN (if present) and otherwise generated as the |
MTA would generate one for a submitted message. |

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The DSN has an RFC 822 header. Trace is mapped in the same |
manner as for a message to |
MTA.ReportTransferEnvelope.trace-information. All other headers |
are used to create a dsn-header-list extension, which is added to |
MTA.ProbeTransferFields.extensions. |
MTA.ReportTransferFields.extensions.

The DSN will have a single 822-MTS SMTP recipient. This is | mapped |
to the %MTA.ReportTransferEnvelope.report-destination- |
name. | MTA.ReportTransferEnvelope.report-destination-name.

The DSN is then treated as a normal MIME message, and an |
X.400 IPM is generated. This IPM is used as |
MTA.PerReportTransferFields.returned-content, and its type is |
used to set MTA.PerReportTransferFields.content-type. The DSN |
body part is mapped as if it was IA5 text/plain. |

All other mappings are made from the DSN body part. A dsn- |
field-list extension is created and added to |
MTA.ReportTransferFields.extensions. This is referred to as the |
per report extension list. The DSN.per-message-fields are mapped |
as follows: |

Each reported recipient is considered in turn, and a |
MTA.PerRecipientReportTransferFields created for each. The |
parameters of this are defaulted as follows: |

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originally-specified-recipient-number |
In general, these are not available, and so are assigned |

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incrementally. |

last-trace-information |
The arrival-time is generated from DSN.arrival-date if |
present, and if not from the Date: of the DSN. |

A dsn-field-list extension is created and added to |
MTA.PerRecipientTransferFields.extensions. This is referred to |
as the per recipient extension list. The |
DSN.per-recipient-fields are mapped as follows |

original-recipient-field |
Mapped to |
MTA.PerRecipientReportTransferFields.originally-intended-recipient-name.|
MTA.PerRecipientReportTransferFields.originally-intended-recipient-name.

final-recipient-field |
Mapped to |
MTA.PerRecipientReportTransferFields.actual-recipient-name. |

action-field |
If this is set to "failed", a non-delivery report is |
generated. Otherwise a delivery report is generated. Bit |
one or two of |
MTA.PerRecipientTransferFields.per-recipient-indicators is |
set accordingly. This also controls the encoding of |
MTA.PerRecipientTransferFields.last-trace-information, and |
the selection of the report type. |

remote-mta-field |

diagnostic-code-field |

last-attempt-date-field |

will-retry-until-field |

extension-field |

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extension-field

other |
All of these fields are added to the per report recipient extension |
list. |

5.1.8.4. Status Value Mappings |

Status values are mapped to X.400 reason and diagnostic codes as |
follows. |

DSN code Meaning X400 C/D code Meaning |

X.0.0 Other status 1/None

X.1.0 Other Address Status 1/None
X.1.1 Bad mailbox address 1/0 Unrecognized
X.1.2 Bad system address 1/0 Unrecognized
X.1.3 Bad mailbox address syntax 1/0 Unrecognized
X.1.4 Mailbox address ambiguous 1/1

X.2.0 Other or undefined mailbox status 1/None
X.2.1 Mailbox disabled, not accepting 1/4 Recipient unavailable
X.2.2 Mailbox full 1/4
X.2.3 Message length exceeds admin limit. 1/7 Content too long
X.2.4 Mailing list expansion problem 1/30 DL expansion failure

X.3.0 Other or undefined system status 0/None
X.3.1 System full 1/2 MTS congestion
X.3.2 System not accepting network messages 1/2 MTS congestion
X.3.3 System not capable of selected feat 1/18 Unsupp. crit. func
X.3.4 Message too big for system 1/7

X.4.0 Other or undefined network or routing 0/None
X.4.1 No answer from host 0/None
X.4.2 Bad connection 0/None
X.4.3 Routing server failure 6/None Directory op unsucc.
X.4.4. Unable to route 0/None
X.4.5 Network congestion 1/2 MTS congest.
X.4.6 Routing loop detected 1/3
X.4.7 Delivery time expired 1/5

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X.5.0 Other or undefined protocol status 1/None

X.5.1 Invalid command 1/14 Protocol viol.
X.5.2 Syntax error 1/14
X.5.3 Too many recipients 1/16
X.5.4 Invalid command arguments 1/14
X.5.5 Wrong protocol version 1/18 Unsupp.crit.func

X.6.0 Other or undefined media error 2/None Conv. not perf
X.6.1 Media not supported 1/6 EIT unsupp.
X.6.2 Conversion required and prohibited 1/9
X.6.3 Conversion required but not supported 2/8
X.6.4 Conversion with loss performed POSITIVE only

X.7.0 Other or undefined security status 1/46
X.7.1 Delivery not authorized, message ref 1/29 No DL submit perm
X.7.2 Mailing list expansion prohibited 1/28
X.7.3 Security conversion req but not poss 1/46 Secure mess. error
X.7.4 Security features not supported 1/46
X.7.5 Cryptographic failure 1/46
X.7.6 Cryptographic algorithm not supported 1/46
X.7.7 Message integrity failure 1/46

5.1.8.5. DSNs that originated in X.400 |

The mapping of X.400 delivery reports to DSNs will in general |
provide sufficient information to make a useful reverse mapping. |
Messages will often be mapped multiple times, commonly due to |
forwarding messages and to distribution lists. Multiple |
mappings for delivery reports will be a good deal less common. |
For this reason, the reverse mapping of the X.400 DSN extensions |
defined in MIXER is optional.

5.2. Return of Contents

It is not clear how widely supported the X.400 return of contents
service will be. Experience with X.400(1984) suggests that
support of this service may not be universal. As this service is
expected in the RFC 822 world, two approaches are specified. The
choice will depend on the use of X.400 return of contents withing
the X.400 community being serviced by the gateway.

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In environments where return of contents is widely
supported, content return can be requested as a service. The
content return service can then be passed back to the end (RFC
822) user in a straightforward manner.

In environments where return of contents is not widely
supported, a gateway must make special provision to handle return
of contents. For every message passing from RFC 822 -> X.400,
content return request will not be requested, and report request
always will be. When the delivery report comes back, the gateway
can note that the message has been delivered to the recipient(s)
in question. If a non-delivery report is received, a meaningful
report (containing some or all of the original message) can be
sent to the 822-MTS originator. If no report is received for a
recipient, a (timeout) failure notice shall be sent to the
822-MTS originator. The gateway may retransmit the X.400 message
if it wishes. When this approach is taken, routing must be set
up so that error reports are returned through the same MTA.
This approach may be difficult to use in conjunction with some
routing strategies. *

5.3. | X.400 -> RFC 822: Detailed Mappings

5.3.1. Basic Approach

A single RFC 822 message is generated from the incoming IP
Message, Report, or IP Notification. All IPMS.BodyParts are
mapped onto a single RFC 822 body. Other services are mapped
onto RFC 822 header fields. Where there is no appropriate
existing field, new fields are defined for IPMS, MTS and MTA
services.

The gateway mechanisms will correspond to MTS Delivery. As
with submission, there are aspects where the MTA (transfer)
services are also used. In particular, there is an optimisation |
to allow for multiple 822-MTS SMTP recipients.

5.3.2. RFC 822 Settings

An RFC 822 Service requires to have Message has a number of mandatory fields in the RFC |
822 Header. Some 822-MTS SMTP services mandate specification of an 822-MTS SMTP
Originator. Even in cases where this is optional, it is usually
desirable to specify a value. The

Kille [page 101]

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MIXER DRAFT Version 2.1 following defaults are
defined, which shall be used if the mappings specified do not
derive a value:

822-MTS |

SMTP Originator |
If this is not generated by the mapping (e.g., for a
Delivery Report), a value pointing at a gateway
administrator shall be assigned.

Date:
A value will always be generated

From: |
If this is not generated by the mapping, it is assigned
equal to the 822-MTS SMTP Originator. If this is gateway generated, |
an appropriate 822.phrase shall be added.

At least one recipient field

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If no recipient fields are generated, a field "To: list:;",
shall be added.

This will ensure minimal RFC 822 compliance. When generating RFC
822 headers, folding may be used. It is recommended to do this,
following the guidelines of RFC 822.

5.3.3. Basic Mappings

5.3.3.1. Encoded Information Types

This mapping from MTS.EncodedInformationTypes is needed in
several disconnected places. EBNF is defined as follows:

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encoded-info = 1#encoded-type

encoded-type = built-in-eit / object-identifier

built-in-eit = "Undefined" ; undefined (0)
/ "Telex" ; tLX (1)
/ "IA5-Text" ; iA5Text (2)
/ "G3-Fax" ; g3Fax (3)
/ "TIF0" ; tIF0 (4)
/ "Teletex" ; tTX (5)
/ "Videotex" ; videotex (6)
/ "Voice" ; voice (7)
/ "SFD" ; sFD (8)
/ "TIF1" ; tIF1 (9)

MTS.EncodedInformationTypes is mapped onto EBNF.encoded-info.
MTS.EncodedInformationTypes.non-basic-parameters is ignored.
Built in types are mapped onto fixed strings (compatible with
X.400(1984) and RFC 987), and other types are mapped onto
EBNF.object-identifier.

5.3.3.2. Global Domain Identifier

The following simple EBNF is used to represent
MTS.GlobalDomainIdentifier:

global-id = std-or-address

This is encoded using the std-or-address syntax, for the

Kille [page 103]

RFC 1327bis
MIXER DRAFT Version 2.2

attributes within the Global Domain Identifier.

5.3.4. Mappings from the IP Message

Consider that an IPM has to be mapped to RFC 822. The IPMS.IPM
comprises an IPMS.IPM.heading and IPMS.IPM.body. The heading is
considered first. Some EBNF for new fields is defined:

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ipms-field = "Obsoletes" ":" 1#msg-id
/ "Expiry-Date" ":" date-time
/ "Reply-By" ":" date-time
/ "Importance" ":" importance
/ "Sensitivity" ":" sensitivity
/ "Autoforwarded" ":" boolean
/ "Incomplete-Copy" ":"
/ "Language" "Content-Language" ":" 1#language |
/ "Message-Type" ":" message-type
/ "Discarded-X400-IPMS-Extensions" ":" 1#object-identifier| 1#object-identifier
/ "Autosubmitted" ":" autosubmitted |

importance = "low" / "normal" / "high"

sensitivity = "Personal" / "Private" /
"Company-Confidential"

language = 2*ALPHA [ language-description ]
language-description = printable-string

message-type = "Delivery Report" |
/ "InterPersonal Notification"
/ "Multiple Part"

autosubmitted = "not-auto-submitted"
/ "auto-generated"
/ "auto-replied"
/ "auto-forwarded"

Kille [page 104]

RFC 1327bis
MIXER DRAFT Version 2.2

The mappings and actions for the IPMS.Heading is are now specified |
for each element. Addresses, Addresses and Message Identifiers are mapped
according to Chapter 4. Other mappings are explained, or are
straightforward (algorithmic). If a field with addresses
contains zero elements, it should be discarded, except for |
IPMS.Heading.blind-copy-recipients, which can be mapped onto BCC:
(the only RFC 822 field which allows zero recipients).

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MIXER DRAFT Version 2.1

IPMS.Heading.this-IPM
Mapped to "Message-ID:".

IPMS.Heading.originator
If IPMS.Heading.authorizing-users is present this is mapped
to Sender:, if not to "From:".

IPMS.Heading.authorizing-users
Mapped to "From:".

IPMS.Heading.primary-recipients
Mapped to "To:".

IPMS.Heading.copy-recipients
Mapped to "Cc:".

IPMS.Heading.blind-copy-recipients
Mapped to "Bcc:".

IPMS.Heading.replied-to-ipm
Mapped to "In-Reply-To:".

IPMS.Heading.obsoleted-IPMs
Mapped to the extended RFC 822 field "Obsoletes:"

IPMS.Heading.related-IPMs
Mapped to "References:".

IPMS.Heading.subject
Mapped to "Subject:". The contents are converted to ASCII |
or T.61 (as defined in Section 3.5). Any CRLF are not
mapped, but are used as points at which the subject field
must be folded.

IPMS.Heading.expiry-time
Mapped to the extended RFC 822 field "Expiry-Date:".

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RFC 1327bis
MIXER DRAFT Version 2.2

IPMS.Heading.reply-time
Mapped to the extended RFC 822 field "Reply-By:".

IPMS.Heading.reply-recipients
Mapped to "Reply-To:".

IPMS.Heading.importance

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MIXER DRAFT Version 2.1
Mapped to the extended RFC 822 field "Importance:".

IPMS.Heading.sensitivity
Mapped to the extended RFC 822 field "Sensitivity:".

IPMS.Heading.autoforwarded
Mapped to the extended RFC 822 field "Autoforwarded:".

The standard extensions (Annex H of X.420 / ISO 10021-7) are
mapped as follows:

incomplete-copy
Mapped to the extended RFC 822 field "Incomplete-Copy:". |

language |
Mapped to the RFC 822 field "Content-Language:", defined in |
RFC 1766 [13]. [8]. This mapping may be made without loss of |
information. |

auto-submitted |
Map to the extended RFC 822 field "Autosubmitted:".

If the RFC 822 extended header is found, this shall be
mapped onto an RFC 822 header, as described in Section 5.1.2.

If a non-standard extension is found, it shall be discarded,
unless the gateway understands the extension and can perform an
appropriate mapping onto an RFC 822 header field. If extensions
are discarded, the list is indicated in the extended RFC 822
field "Discarded-X400-IPMS-Extensions:". |

5.3.4.1. Mapping the IPMS Body |

The IPMS.Body is mapped into the RFC 822 message body. If the |
IPMS.Body consists of a single IPMS.Bodypart, there are three |
possibilities. |

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RFC 1327bis
MIXER DRAFT Version 2.2

1. If it is of type IPMS.IA5Text, then this is mapped directly |
and no MIME encoding is used. |

2. If it is of type IPMS.MessageBodyPart, then a MIME message |
with content type message/rfc822 is generated, following the |
mappings described for IPMS.BodyPart given below. below, except in |

Kille [page 106]

INTERNET DRAFT
MIXER DRAFT Version 2.1
the case where a multipart-message heading extension is |
present. In the latter case the mapping of 5.1 shall be |
reversed.

3. The mapping of other body parts is specified below. |

If the IPMS.Body contains multiple IPMS.BodyPart fields, then a |
MIME message of content type multipart is generated. If all of |
the body parts are messages, then this is multipart/digest. |
Otherwise it is multipart/mixed. The components of the multipart |
are generated in the same order as in the IPMS.Body. Body parts |
which are not messages are mapped according to RFC 1494. 1494bis. |

To map an IPMS.MessageBodyPart, the full X.400 -> RFC 822 |
mapping is recursively applied, to generate an RFC 822 Message.
If present, the IPMS.MessageBodyPart.parameters.delivery-envelope
is used for the MTS Abstract Service Mappings. If present, the
IPMS.MessageBodyPart.parameters.delivery-time is mapped to the
extended RFC 822 field "Delivery-Date:". |

To support X.400(1984) mappings of Internet Messages, the |
following procedure shall also be followed. If there is more |
than one body part, and the first body part is IA5 starts with |
the string "RFC-822-Headers:" as the first line, then the |
remainder of this body part shall be appended to the RFC 822 |
header. RFC 822 |
header. This relies that this body part has been generated |
according to Appedix B of MIXER. A gateway shall check the |
consistency and syntax of this body part, to ensure that the |
resulting message is conformant.

5.3.4.2. Mapping Body Parts |

X.400 and MIME define extensible approaches for body parts, and |
the ability to map a specific body part depends on the gateway's |
knowledge. Mapping of all standard X.400 body parts, and some |
extended body parts is defined in RFC 1494bis. |

The case of File Transfer Body Part (FTBP) is described |

Kille [page 107]

RFC 1327bis
MIXER DRAFT Version 2.2

below. |

Where no mapping is known by the gateway, it may choose to |
drop the body part, or reject the message. It may also |
encapsulate the body part in a mechanism which can be used for |
any extended X.400 body part. This is specified below. The |
option will depend on the gateway configuration and its knowledge |
of the recipient capabilities. |

5.3.4.3. File Transfer Body Part |

X.400 specifies a file transfer body part (FTBP). Generic |
mapping of FTBP is beyond the scope of MIXER. EMA have defined |

Kille [page 107]

INTERNET DRAFT
MIXER DRAFT Version 2.1
a profile of FTBP to carry attachments . [28]. MIXER defines a
mapping | of FTBP to MIME, which is intended for use in conjunction
with | this profile. FTBP is used to carry various pieces of |
information associated with an attachment. The key mapping will |
be to correctly convert the contents of the attachment. This |
specification also provides a mechanism for mapping the |
parameters which EMA have recommended to be used in version 1.4 |
of the specification. A BNF is defined below: |

ftbp-field = "FTBP-Pathname" ":" *text
/ "FTBP-Object-Size" ":" integer |
/ "FTBP-Creation-Date" ":" date-time
/ "FTBP-Modification-Date" ":" date-time
"FTBP-Read-Date" ":" date-time

Some parameters are encoded as graphical string. strings. To map |
these to ASCII, those characters that map directly are mapped, |
and others are translated to "?". This simple non-reversible |
mapping is seen as appropriate for the application, and in line |
with the spirit of the EMA profile. |

Mapping of the data will be dependent on the attachment, its |
encoding, and the MIME representation. These cannot be |
specified here. |

Other FTBP Parameters are mapped as follows: |

FileTransferParameters.environment.user-visible-string |
This is mapped to the "Content-Descriptor:" header. |

The following elements of FileTransferParameters.file-attributes |

Kille [page 108]

RFC 1327bis
MIXER DRAFT Version 2.2

are mapped as follows: |

pathname |
Mapped to "FTBP-Pathname". "Content-Dispostion:", as defined in RFC 1806 |
[33]. The EBNF.disposition-type is set to "attachment", and |
the filename is included as a parameter. For example: |

Content-Disposition: attachment; filename=/var/joe/dodo.doc

It is expected that only the | incomplete option will be
found, but the mapping is used for | either variant. The
separator between multiple components | is "/". |

date-and-time-of-creation |
Mapped to "FTBP-Creation-Date:". |

date-and-time-of-last-modification |

Kille [page 108]

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MIXER DRAFT Version 2.1
Mapped to "FTBP-Modification-Date:". |

date-and-time-of-last-read-access |
Mapped to "FTBP-Read-Date:". |

object-size |
Mapped to "FTBP-Object-Size:". |

5.3.4.4. Tunnelling X.400 Body Parts |

This section specifies a generic mechanism to map X.400 body |
parts to a MIME content. This allows for the body part to be |
tunnelled through MIME. It may also be used directly by an |
appropriately configured MIME UA. |

This content-type is defined to carry any X.400 extended |
body part. The mapping of all standard X.400 body parts is |
defined in RFC1494bis. The content-type field is |
"application/x400-bp". The parameter is defined by the EBNF: |

mime-parameter = "bp-type=" object-identifier

The EBNF.object-identifier is set to the OBJECT IDENTIFIER |
from IPMS.body.externally-defined.data.direct-reference . |

For example, a Videotex body part will have

Kille [page 109]

RFC 1327bis
MIXER DRAFT Version 2.2

Content-type=application/x400-bp; bp-type=2.6.1.4.5 |

The body contains the raw ASN.1 IPM.body octet stream, |
including the initial tag octet. The content may use a content- |
transfer-encoding of either base64 or quoted-printable when |
carried in 7-bit MIME. It is recommended to use the one which |
gives the more compact encoding of the data. If this cannot be |
determined, Base64 is recommended. No attempt is made to turn |
the parameters of Extended Body Parts into MIME parameters, as |
this cannot be done in a general manner.

Standard X.400 body parts may not be encoded directly by |
this mechanism, but may be encoded indirectly by first |
translating to the extended representation. |

Kille [page 109]

INTERNET DRAFT
MIXER DRAFT Version 2.1

Editor's |
I've changed this from RFC 1494. I think that is much |
cleaner and better. We should review this choice. | *

5.3.4.5. Example Message |

An example message, illustrating a number of aspects is given
below.

Kille [page 110]

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RFC 1327bis
MIXER DRAFT Version 2.1 2.2

Received: from mhs-relay.ac.uk by bells.cs.ucl.ac.uk via JANET with NIFTP *
id <7906-0@bells.cs.ucl.ac.uk>; Thu, 30 May 1991 18:24:55 +0100
X400-Received: by mta "mhs-relay.ac.uk" in /PRMD=uk.ac/ADMD= /C=gb/; Relayed;
Thu, 30 May 1991 18:23:26 +0100
X400-Received: by /PRMD=HMG/ADMD=GOLD 400/C=GB/; Relayed;
Thu, 30 May 1991 18:20:27 +0100
Message-Type: Multiple Part
Date: Thu, 30 May 1991 18:20:27 +0100
X400-Originator: Stephen.Harrison@gosip-uk.hmg.gold-400.gb
X400-MTS-Identifier:
[/PRMD=HMG/ADMD=GOLD 400/C=GB/;PC1000-910530172027-57D8]
Original-Encoded-Information-Types: ia5, undefined ia5 |
X400-Content-Type: P2-1984 (2)
X400-Content-Identifier: Email Problems |
From: Stephen.Harrison@gosip-uk.hmg.gold-400.gb (Tel +44 71 217 3487)
Message-ID: <PC1000-910530172027-57D8*@MHS>
To: Jim Craigie <NTIN36@gec-b.rutherford.ac.uk>, |
Tony Bates <tony@ean-relay.ac.uk>, |
Steve Kille <S.Kille@cs.ucl.ac.uk> |
Subject: Email Problems
Sender: Stephen.Harrison@gosip-uk.hmg.gold-400.gb
MIME-Version: 1.0 |
Content-Type: multipart/mixed; boundary=boundary-1 |

--boundary-1 |
Content-Type: text/plain; charset=US-ASCII |

Hope you gentlemen....... *

Regards,

Stephen Harrison
UK GOSIP Project

..... continued on next page

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RFC 1327bis
MIXER DRAFT Version 2.1 2.2

--boundary-1 |
Content-Type: message/rfc822 |

From: Urs Eppenberger <Eppenberger@verw.switch.ch>
Message-ID:
<562*/S=Eppenberger/OU=verw/O=switch/PRMD=SWITCH/ADMD=ARCOM/C=CH/@MHS>
To: "Stephen.Harrison" <Stephen.Harrison@gosip-uk.hmg.gold-400.gb>
Cc: kimura@bsdarc.bsd.fc.nec.co.jp
Subject: Response to Email link
Content-Type: multipart/mixed; boundary=boundary-2 |

--boundary-2 |

Dear Mr Harrison......

--boundary-2

--boundary-2-- |

--boundary-1

--boundary-1-- |

5.3.5. Mappings from an IP Notification

Because of the service setting, IP Notifications will not usually |
need to be mapped by a MIXER gateway. A message is generated,
with the following fields:

From:
Set to the IPMS.IPN.ipn-originator.

To: Set to the recipient from MTS.MessageSubmissionEnvelope.
If there have been redirects, the original address should be
used.

Subject:
Set to the string "X.400 Inter-Personal Notification" for a
receipt notification and to "X.400 Inter-Personal
Notification (failure)" for a non-receipt notification.

Message-Type:
Set to "InterPersonal Notification"

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RFC 1327bis
MIXER DRAFT Version 2.1 2.2

Set to "InterPersonal Notification"

References:
Set to IPMS.IPN.subject-ipm |

Discarded-X400-IPMS-Extensions: |
Used for any discarded IPN extensions.

The following EBNF is defined for the body of the Message. This
format is defined to ensure that all information from an
interpersonal notification is available to the end user in a
uniform manner.

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RFC 1327bis
MIXER DRAFT Version 2.1 2.2

ipn-body-format = ipn-description <CRLF> *
[ ipn-extra-information <CRLF> ]
[ ipn-content-return ]

ipn-description = ipn-receipt / ipn-non-receipt

ipn-receipt = "Your message to:" preferred-recipient <CRLF>
"was received at" receipt-time <CRLF> <CRLF>
"This notification was generated"
acknowledgement-mode <CRLF>
"The following extra information was given:" <CRLF>
ipn-suppl <CRLF>

ipn-non-receipt "Your message to:"
preferred-recipient <CRLF>
ipn-reason

ipn-reason = ipn-discarded / ipn-auto-forwarded

ipn-discarded = "was discarded for the following reason:"
discard-reason <CRLF>

ipn-auto-forwarded = "was automatically forwarded." <CRLF>
[ "The following comment was made:"
auto-comment ]

ipn-extra-information =
"The following information types were converted:"
encoded-info

ipn-content-return = "The Original Message is not available"
/ "The Original Message follows:"

preferred-recipient = mailbox
receipt-time = date-time
auto-comment = printablestring
ipn-suppl = printablestring

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RFC 1327bis
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discard-reason = "Expired" / "Obsoleted" /
"User Subscription Terminated"

acknowledgement-mode = "Manually" / "Automatically"

The mappings for elements of the common fields of IPMS.IPN
(IPMS.CommonFields) onto this structure and the message header
are:

subject-ipm
Mapped to "References:"

ipn-originator
Mapped to "From:".

ipn-preferred-recipient
Mapped to EBNF.preferred-recipient

conversion-eits
Mapped to EBNF.encoded-info in EBNF.ipn-extra-information

The mappings for elements of IPMS.IPN.non-receipt-fields
(IPMS.NonReceiptFields) are:

non-receipt-reason
Used to select between EBNF.ipn-discarded and
EBNF.ipn-auto-forwarded

discard-reason
Mapped to EBNF.discard-reason

auto-forward-comment
Mapped to EBNF.auto-comment

returned-ipm
This applies only to non-receipt notifications.
EBNF.ipn-content-return should always be omitted for receipt
notifications, and always be present in non-receipt
notifications. If present, the second option of
EBNF.ipn-content-return is chosen, and the message is |
included. In this case, the message is formatted as |
multipart/mixed, and the returned message included as |
message/rfc822 after the text body part. Otherwise the first |

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RFC 1327bis
MIXER DRAFT Version 2.1 2.2

option is chosen.

The mappings for elements of IPMS.IPN.receipt-fields
(IPMS.ReceiptFields) are:

receipt-time
Mapped to EBNF.receipt-time

acknowledgement-mode
Mapped to EBNF.acknowledgement-mode

suppl-receipt-info
Mapped to EBNF.ipn-suppl

An example notification is:

From: Steve Kille <steve@cs.ucl.ac.uk>
To: Julian Onions <jpo@computer-science.nottingham.ac.uk>
Subject: X.400 Inter-personal Notification
Message-Type: InterPersonal Notification
References: <1229.614418325@UK.AC.NOTT.CS>
Date: Wed, 21 Jun 89 08:45:25 +0100

Your message to: Steve Kille <steve@cs.ucl.ac.uk>
was automatically forwarded.
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5.3.6. Mappings from the MTS Abstract Service

This section describes the MTS mappings for User Messages (IPM
and IPN). This mapping is defined by specifying the mapping of
MTS.MessageDeliveryEnvelope. The following extensions to RFC 822
are defined to support this mapping:

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mts-field = "X400-MTS-Identifier" ":" mts-msg-id
/ "X400-Originator" ":" mailbox
/ "X400-Recipients" ":" 1#mailbox
/ "Original-Encoded-Information-Types" ":"
encoded-info
/ "X400-Content-Type" ":" mts-content-type
/ "Content-Identifier" ":" printablestring
/ "Priority" ":" priority
/ "Originator-Return-Address" ":" 1#mailbox
/ "DL-Expansion-History" ":" mailbox ";" date-time ";"
/ "Conversion" ":" prohibition
/ "Conversion-With-Loss" ":" prohibition
/ "Requested-Delivery-Method" ":"
1*( labelled-integer )
/ "Delivery-Date" ":" date-time
/ "Discarded-X400-MTS-Extensions" ":"
1#( object-identifier / labelled-integer )| )

prohibition = "Prohibited" / "Allowed"

mts-msg-id = "[" global-id ";" *text "]"

mts-content-type = "P2" / labelled-integer
/ object-identifier |

priority = "normal" / "non-urgent" / "urgent"

The mappings for each element of MTS.MessageDeliveryEnvelope can
now be considered.

MTS.MessageDeliveryEnvelope.message-delivery-identifier
Mapped to the extended RFC 822 field "X400-MTS-Identifier:".

MTS.MessageDeliveryEnvelope.message-delivery-time
Discarded, as this time will be represented in an
appropriate trace element.

The mappings for elements of
MTS.MessageDeliveryEnvelope.other-fields
(MTS.OtherMessageDeliveryFields) are:

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content-type
Mapped to the extended RFC 822 field "X400-Content-Type:".
The string "P2" is retained for backwards compatibility with
RFC 987. This shall not be generated, and either the
EBNF.labelled-integer or EBNF.object-identifier encoding
used.

originator-name
Mapped to the 822-MTS SMTP originator, and to the extended RFC 822 |
field "X400-Originator:". This is described in
Section 4.6.2.

original-encoded-information-types
Mapped to the extended RFC 822 field
"Original-Encoded-Information-Types:".

priority
Mapped to the extended RFC 822 field "Priority:".

delivery-flags
If the conversion-prohibited bit is set, add an extended RFC
822 field "Conversion:".

this-recipient-name and other-recipient-names

originally-intended-recipient-name
The handling of these elements is described in
Section 4.6.2.

converted-encoded-information-types
Discarded, as it
Discarded. This information will always be IA5 only. mapped in the trace. |

message-submission-time
Mapped to Date:.

content-identifier
Mapped to the extended RFC 822 field |
"X400-Content-Identifier:". In RFC 1327, this was |
"Content-Identifier:". This has been changed to avoid |
confusion with MIME defined fields. Gateways which reverse |
map, may support the old field.

If any extensions
(MTS.MessageDeliveryEnvelope.other-fields.extensions) are

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present, and they are marked as critical for transfer or
delivery, then the message shall be rejected. The extensions
(MTS.MessageDeliveryEnvelope.other-fields.extensions) are mapped
as follows.

conversion-with-loss-prohibited
If set to
MTS.ConversionWithLossProhibited.conversion-with-loss-prohibited,
then add the extended RFC 822 field "Conversion-With-Loss:".

requested-delivery-method
Mapped to the extended RFC 822 field
"Requested-Delivery-Method:".

originator-return-address
Mapped to the extended RFC 822 field
"Originator-Return-Address:".

physical-forwarding-address-request
physical-delivery-modes
registered-mail-type
recipient-number-for-advice
physical-rendition-attributes
physical-delivery-report-request
physical-forwarding-prohibited

These elements are only appropriate for physical delivery.
They are represented as comments in the "X400-Recipients:"
field, as described in Section 4.6.2.2.

originator-certificate
message-token
content-confidentiality-algorithm-identifier
content-integrity-check
message-origin-authentication-check
message-security-label
proof-of-delivery-request

These elements imply use of security services not available
in the RFC 822 environment. If they are marked as critical
for transfer or delivery, then the message shall be
rejected. Otherwise they are discarded.

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redirection-history
This is described in Section 4.6.2.

dl-expansion-history
Each element is mapped to the extended RFC 822 field
"DL-Expansion-History:". They shall be ordered in the
message header, so that the most recent expansion comes
first (same order as trace).

If any MTS (or MTA) Extensions not specified in X.400 are
present, and they are marked as critical for transfer or
delivery, then the message shall be rejected. If they are not so
marked, they can safely be discarded. The list of discarded
fields shall be indicated in the extended header
"Discarded-X400-MTS-Extensions:".

5.3.7. Mappings from the MTA Abstract Service

There are some mappings at the MTA Abstract Service level which
are done for IPM and IPN. These can be derived from
MTA.MessageTransferEnvelope. The reasons for the mappings at
this level, and the violation of layering are:

- Allowing for multiple recipients to share a single RFC 822
message

- Making the X.400 trace information available on the RFC 822
side

- Making any information on deferred delivery available

The 822-MTS SMTP recipients are calculated from the full list of X.400 |
recipients. This is all of the members of
MTA.MessageTransferEnvelope.per-recipient-fields being passed
through the gateway, where the responsibility bit is set. In
some cases, a different RFC 822 message would be calculated for
each recipient, due to differing service requests for each |
recipient. As discussed in 4.6.2.2, this specification allows |
either for multiple messages to be generated, or for the per-
recipient information to be discarded.

The following EBNF is defined for extended RFC 822 headers:

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mta-field = "X400-Received" ":" x400-trace
/ "Deferred-Delivery" ":" date-time
/ "Latest-Delivery-Time" ":" date-time

x400-trace = "by" md-and-mta ";"
[ "deferred until" date-time ";" ]
[ "converted" "(" encoded-info ")" ";" ]
[ "attempted" md-or-mta ";" ]
action-list
";" arrival-time

md-and-mta = [ "mta" mta "in" ] global-id
mta = word
arrival-time = date-time

md-or-mta = "MD" global-id
/ "MTA" mta

Action-list = 1#action
action = "Redirected"
/ "Expanded"
/ "Relayed"
/ "Rerouted"

Note the EBNF.mta is encoded as 822.word. If the character |
set does no not allow encoding as 822.atom, the 822.quoted-string
encoding is used.

If MTA.PerMessageTransferFields.deferred-delivery-time is
present, it is used to generate a Deferred-Delivery: field. For
some reason, X.400 does not make this information available at
the MTS level on delivery. X.400 profiles, and in particular the
CEN/CENELEC profile for X.400(1984) [36], [32], specify that this
element must be supported at the first MTA. If it is not, the
function may optionally be implemented by the gateway: that is,
the gateway may hold the message until the time specified in the

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protocol element. Thus, the value of this element will usually
be in the past. For this reason, the extended RFC 822 field is
primarily for information.

Merge MTA.PerMessageTransferFields.trace-information, and
MTA.PerMessageTransferFields.internal-trace-information to
produce a single ordered trace list. If Internal trace from
other management domains has not been stripped, this may require
complex interleaving. Where an element of internal trace and
external trace are identical, except for the MTA in the internal
trace, only the internal trace element shall be presented. Use
this to generate a sequence of "X400-Received:" fields. The only
difference between external trace and internal trace will be the
extra MTA information in internal trace elements.

When generating an RFC 822 message all trace fields (X400-
Received and Received) shall be at the beginning of the header,
before any other fields. Trace shall be in chronological order,
with the most recent element at the front of the message. This
ordering is determined from the order of the fields, not from
timestamps in the trace, as there is no guarantee of clock
synchronisation. A simple example trace (external) is:

X400-Received: by /PRMD=UK.AC/ADMD=Gold 400/C=GB/ ; Relayed ;
Tue, 20 Jun 89 19:25:11 +0100

A more complex example (internal):

X400-Received: by mta "UK.AC.UCL.CS" in /PRMD=UK.AC/ADMD=Gold 400/C=GB/ ;
deferred until Tue, 20 Jun 89 14:24:22 +0100 ;
converted (undefined, g3fax) ; attempted /ADMD=Foo/C=GB/ ; |
Relayed, Expanded, Redirected ; Tue, 20 Jun 89 19:25:11 +0100

5.3.8. Mappings from Report Delivery

Delivery reports are mapped at the MTS service level. This means
that only reports destined for the MTS user will be mapped. Some |
additional services are also taken from the MTA service. X.400 |

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Delivery Reports are Mapped onto Delivery Status Notifications, |
as defined by NOTARY [33]. [29].

5.3.8.1. MTS Mappings

A Delivery Report service will be represented as
MTS.ReportDeliveryEnvelope, which comprises of per-report-fields
(MTS.PerReportDeliveryFields) and per-recipient-fields.

A message of type delivery-status is generated with the following |
fields:

From:
An administrator at the gateway system. This is also the
822-MTS |
SMTP originator.

To: A mapping of the
MTA.ReportTransferEnvelope.report-destination-name. This is |
also the 822-MTS SMTP recipient.

Message-Type:
Set to "Delivery Report". This is strictly redundant, but |
retained for backwards compatibility with RFC 1327.

Subject:
The EBNF for the subject line is:

subject-line = "Delivery-Report" "(" status ")"
[ "for" destination ]

status = "success" / "failure" / "success and failures"

destination = mailbox / "MTA" word

The subject is intended to give a clear indication as to the |
nature of the message, and summarise its contents. EBNF.status is |
set according to whether the reports are all successes, all |
failures, or a mixture. The EBNF.destination is used to indicate |
the addresses in the reports. If the report is for a single |
address, EBNF.mailbox is used to give the RFC 822 representation |
of the address. If all of the reports share a common MTA this is |
included in EBNF.word. A common MTA is determined from the |

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delivery report's trace. |

The format of the body of the message follows the NOTARY |
delivery status notification format, and is defined to ensure |
that all information is conveyed to the RFC 822 user in a
consistent manner. The format is structured as if it was a |
message coming from the gateway, with three body parts. The first |
body part is ASCII text structured as follows:

1. A few lines giving keywords to indicate the original
message.

2. A human summary of the status of each recipient being
reported on. |

The second body part is the NOTARY delivery status |
notification, which contains detailed information extracted from |
the report. This information may be critical to diagnosing an
obscure problem. |

This body part may be omitted in positive DRs. For RFC |
1327, this was recommended as appropriate for most gateways. As |
NOTARY becomes more widely adopted, this will make less sense. |
It is likely that this body part will be mandatory in future |
versions of this specification. |

The third (optional) body part contains the returned message |
(return of content). This structure is useful to the RFC 822 |
recipient, as it enables the original message to be extracted. |
It shall be included if the original message is available. |

The enclosing message is a MIME message of content type |
multipart/report, with report-type=delivery-status. The first |
body part containing the user oriented description is of type |
text/plain. The format of this body part is defined below as |
EBNF.dr-user-info.

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dr-user-info = dr-summary <CRLF> |
dr-recipients <CRLF>
dr-content-return *

dr-content-return = "The Original Message is not available"
/ "The Original Message follows:"

dr-summary = "This report relates to your message:" <CRLF>
content-correlator <CRLF> <CRLF>
"of" date-time <CRLF> <CRLF>

dr-recipients = *(dr-recipient <CRLF> <CRLF>)

dr-recipient = dr-recip-success / dr-recip-failure

dr-recip-success =
"Your message was successfully delivered to:"
mailbox "at" date-time

dr-recip-failure = "Your message was not delivered to:"
mailbox <CRLF>
"for the following reason:" *word

report-point = [ "mta" word "in" ] global-id |
content-correlator = *word |

EBNF.dr-summary |
The EBNF.content-correlator is taken from the content |
correlator (or content identifier if there is no content |
correlator) and the EBNF.date-time from the trace, as |
described below. LWSP may be added to improve the layout of |
the body part. |

EBNF.dr-recipients |
There is an element for each recipient in the delivery |
report. In each case, EBNF.mailbox is taken from the RFC |
822 form of the originally specified recipient, which is |
taken from the originally specified recipient element if |
present or from the actual recipient. When reporting |

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success, the message delivery time is used to derive |
EBNF.date-time. When reporting failure, the information |
includes a human readable interpretation of the X.400 |
diagnostic and reason codes, and the supplementary |
information. |

EBNF.dr-content-return |
This is set according to whether or not the content is being |
returned. |

The EBNF of this body part is designed for english-speaking |
users. The language of the strings in the EBNF may be altered. |

The EBNF used in the delivery status notification is: |

dr-per-message-fields = |
/ "X400-Conversion-Date" ":" date-time |
/ "X400-Subject-Submision-Identifier" ":" |
mts-msg-id
/ "X400-Content-Identifier" ":" printablestring |
/ "X400-Content-Type" ":" mts-content-type |
/ "X400-Original-Encoded-Information-Types" ":" |
encoded-info
/ "X400-Originator-and-DL-Expansion-History" ":" |
dl-history
/ "X400-Reporting-DL-Name" ":" mailbox |
/ "X400-Content-Correlator" ":" content-correlator| content-correlator
/ "X400-Recipient-Info" ":" recipient-info |
/ "X400-Subject-Intermediate-Trace-Information" ":"| ":"
x400-trace
/ dr-extensions |

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dr-per-recipient-fields = |
/ "X400-Redirect-Recipient" ":" "x400" ";" std-or| std-or
/ "X400-Mapped-Redirect-Recipient" ":" "rfc822" ";" mailbox| mailbox
/ "X400-Converted-EITs" ":" encoded-info ";" |
/ "X400-Delivery-Time" ":" date-time |
/ "X400-Type-of-MTS-User" ":" labelled-integer |
/ "X400-Last-Trace" ":" [ encoded-info ] date-time |
/ "X400-Supplementary-Info" ":" |
<"> printablestring <"> ";" |
/ "X400-Redirection-History" ":" redirection-comment| redirection-comment
/ "X400-Physical-Forwarding-Address" ":" printablestring| printablestring
/ "X400-Originally-Specified-Recipient-Number" ":"| ":"
integer |
/ dr-extensions |

dr-extensions = "X400-Discarded-DR-Extensions" ":" |
1# (object-identifier / labelled-integer)| labelled-integer)

dl-history = 1#( mailbox "(" date-time ")") |

/ "X400-Diagnostic" ":" labelled-integer |
/ "X400-Reason" ":" labelled-integer |

dr-diagnostic = "Reason" labelled-integer |
[ ";" "Diagnostic" labelled-integer ] |

A body part of type delivery status, as defined by NOTARY, is |
generated. MIXER extends this delivery status notification (DSN) |
specification, by defining additional per message fields in |
EBNF.dr-per-message-fields and additional per recipient fields in |
EBNF.dr-per-recipient-fields. These are used as extensions to |
DSN.per-message-fields and DSN.per-recipient-fields. |

The following DSN.per-message-fields are always generated: |

DSN.reporting-mta-field |
The DSN.mta-name-type is set to "x400", and this string is |
reserved by MIXER. The DSN.mta-name has its syntax |
specified by EBNF.report-point, with the information derived |
from the first element of the DR's trace. |

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DSN.arrival-date-field |
This is derived from the date of the first element of trace |
in the DR.

The following two EBNF.per-message-fields are generated by |
the MIXER gateway: |

DSN.dsn-gateway-field |
The type is set to "dns" and the domain set to the local |
domain of the gateway. |

X400-Conversion-Date: |
The EBNF.date-time is set to the time of the MIXER |
conversion. |

The elements of MTS.ReportDeliveryEnvelope.per-report-fields
are mapped as follows onto the DSN per message fields as follows: |

subject-submission-identifier
Mapped to DSN.original-envelope-id-field. The encoding of |
this MTS Identifier follows the format EBNF.mts-msg-id.

content-identifier
Mapped to X400-Content-Identifier: |

content-type
Mapped to X400-Content-Type: |

original-encoded-information-types
Mapped to X400-Encoded-Info: |

The extensions from
MTS.ReportDeliveryEnvelope.per-report-fields.extensions are
mapped as follows:

originator-and-DL-expansion-history
Mapped to X400-Originator-and-DL-Expansion-History: |

reporting-DL-name
Mapped to X400-Reporting-DL-Name: |

content-correlator
Mapped to X400-Content-Correlator:, provided that the |
encoding is IA5String (this will always be the case).

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message-security-label
reporting-MTA-certificate
report-origin-authentication-check

These security parameters will not be present unless there
is an error in a remote MTA. If they are present, they
shall be discarded in preference to discarding the whole |
report. They shall be listed in the X400-Discarded-DR- |
Extensions: field.

If there are any other DR extensions, they shall also be |
discarded and listed in the X400-Discarded-DR-Extensions: field. |

For each element of
MTS.ReportDeliveryEnvelope.per-recipient-fields, a set of |
DSN.per-recipient-fields is generated. The fields are filled in |
as follows:

actual-recipient-name
If originally-intended-recipient-name is not present present, |
Generate
generate a DSN.final-recipient-field fields, with |
DSN.address-type of "rfc822", and with an RFC 822 mailbox |
generated from the address encoded as specified by NOTARY. |
Also generate a DSN.original-recipient-field field, which |
holds the X.400 representation of the same address. If the |
directory name is present, it should be added as a trailing |
comment in the X.400 form. |

If originally-intended-recipient-name is present Generate an present, generate |
an "X400-Mapped-Redirect-Recipient:" field, with |
DSN.address-type of "rfc822", and with an RFC 822 mailbox |
generated from the address encoded as specified by NOTARY. |
Also generate an X400-Redirect-Recipient:" field, which |
holds the X.400 representation of the same address. If the |
directory name is present, it should be added as a trailing |
comment in the X.400 form.

report
If it is MTS.Report.delivery, then set DSN.action-field to |
"delivered", and set "X400-Delivery-Time:" and |
"X400-Type-of-MTS-User:" from the information in the report. |
DSN.status field is set to "2.0.0". |

If it is MTS.Report.non-delivery, then set DSN.action-field |

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to "failure". DSN.diagnostic-code-field is encoded |
according to the syntax EBNF.dr-diagnostic, with the |
labelled integers set from the reason and diagnotic codes. |
DSN.status-field is derived from the reason and diagnostic |
codes, as described below.

converted-encoded-information-types
Set X400-Converted-EITs: |

originally-intended-recipient
Generate a DSN.final-recipient-field fields, field, with |
DSN.address-type of "rfc822", and with an RFC 822 mailbox |
generated from the address encoded as specified by NOTARY. |
Also generate a DSN.original-recipient-field field, which |
holds the X.400 representation of the same address. If the |
directory name is present, it should be added as a trailing |
comment in the X.400 form.

supplementary-info
Set X400-Supplementary-Info: |

redirection-history
Set X400-Redirection-History: |

physical-forwarding-address
Set X400-Physical-Forwarding-Address: |

recipient-certificate
Discard

proof-of-delivery
Discard

Any unknown extensions shall be discarded, irrespective of |
criticality. All discarded extensions shall be included in a |
"X400-Discarded-DR-Extensions:" field.

The number from the |
MTA.PerRecipientReportTransferFields.originally-specified-recipient-number|
MTA.PerRecipientReportTransferFields.originally-specified-recipient-number
shall be mapped to "X400-Originally-Specified-Recipient-Number:", |
in order to facilitate reverse mapping of delivery reports. |

The original message shall be included in the delivery |
status notification if it is available. The original message will |

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usually be available at the gateway, as discussed in Section 5.2.
If the original message is available, but of erroneous is not a legal message |
format, a dump of the ASN.1 may be included, encoded as |
application/octet-string. This is recommended, but not required. |

Where the original message is included, it shall be encoded |
according to the MIME specifications as content type |
message/rfc822.

5.3.8.2. Status Code Mappings |

This section defines the mappings from X.400 diagnostic and |
status codes to the NOTARY Status field. |

C/D X400 meaning DSN code Means

0/Any Transfer failure (may be temporary) 4.4.0 Other net/route
1/Any Unable to transfer 5.0.0 Other, unknown
2/Any Conversion not performed 5.6.3 Conv not supported
3/Any Physical rendition not performed 5.6.0 Other media error
4/Any Physical delivery not performed 5.1.0 Other address status
5/Any Restricted delivery 5.7.1
6/Any Directory operation unsuccessful 5.4.3 Routing server failure
7/Any Deferred delivery not performed 5.3.3 Not capable

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1/0 Unrecognized O/R name 5.1.1
1/1 Ambiguous O/R name 5.1.4
1/2 MTS congestion 4.3.1
1/3 Loop detected 5.4.6
1/4 Recipient unavailable 4.2.1
1/5 Delivery time expired 4.4.7
1/6 Encoded information types unsupported 5.6.1 Media unsupp.
1/7 Content too long 5.2.3
2/8 Conversion impractical 5.6.3
2/9 Conversion prohibited 5.6.3
1/10 Implicit conversion not subscribed 5.6.3
1/11 Invalid arguments 5.5.2
1/12 Content syntax error 5.5.2
1/13 Size constraint violation 5.5.2
1/14 Protocol violation 5.5.0
1/15 Content type not supported 5.6.1 Media unsupp.
1/16 Too many recipients 5.5.3
1/17 No bilateral agreement 5.4.4
1/18 Unsupported critical function 5.3.3 System not capable
2/19 Conversion with loss prohibited 5.6.2
2/20 Line too long 5.6.0
2/21 Page split 5.6.0
2/22 Pictorial symbol loss 5.6.2
2/23 Punctuation symbol loss 5.6.2
2/24 Alphabetic character loss 5.6.2
2/25 Multiple information loss 5.6.2
1/26 Recipient reassignment prohibited 5.4.0 Undefined net/route
1/27 Redirection loop detected 5.4.6
1/28 DL expansion prohibited 5.7.2
1/29 No DL submit permission 5.7.1 Delivery not authorized
1/30 DL expansion failure 4.2.4
4/31 Physical rendition attrs not supported 5.6.0 Undefined media error
4/32-45 Various physical mail stuff 5.1.0 Other address status
1/46 Secure messaging error 5.7.0 Other security status
2/47 Unable to downgrade 5.3.3 System not capable
0/48 Unable to complete transfer 5.3.4 Message too big
0/49 Transfer attempts limit reached 4.4.7 Delivery time expired

5.3.8.3. MTA Mappings

The single 822-MTS SMTP recipient is constructed from |

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MTA.ReportTransferEnvelope.report-destination-name, using the
mappings of Chapter 4. Unlike with a user message, this
information is not available at the MTS level.

The following additional mappings are made, which results in |
fields in the outer header of the DSN.

MTA.ReportTransferEnvelope.report-destination-name
This is used to generate the To: field.

MTA.ReportTransferEnvelope.identifier
Mapped to the extended RFC 822 field "X400-MTS-Identifier:".
It may also be used to derive a "Message-Id:" field.

MTA.ReportTransferEnvelope.trace-information
and

MTA.ReportTransferEnvelope.internal-trace-information
Mapped onto the extended RFC 822 field "X400-Received:", as
described in Section 5.3.7. |

The following additional mappings are made, which result in per |
message fields in the DSN body part:

MTA.PerRecipientReportTransferFields.last-trace-information
Mapped to X400-Last-Trace:". |

MTA.PerReportTransferFields.subject-intermediate-trace-
information Mapped to |
X400-Subject-Intermediate-Trace-Information:". These fields
are ordered so that the most recent trace element comes
first.

5.3.8.4. Example Delivery Reports

This section contains sample delivery reports. These are the |
same examples used in RFC 1327, and so they also illustrate the |
changes between RFC 1327 and this document. Example Delivery
Report 1:

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Received: from cs.ucl.ac.uk by bells.cs.ucl.ac.uk *
via Delivery Reports Channel id <27699-0@bells.cs.ucl.ac.uk>;
Thu, 7 Feb 1991 15:48:39 +0000
From: UCL-CS MTA <postmaster@cs.ucl.ac.uk>
To: S.Kille@cs.ucl.ac.uk
Subject: Delivery Report (failure) for H.Hildegard@bbn.com
Message-Type: Delivery Report
Date: Thu, 7 Feb 1991 15:48:39 +0000
Message-ID: <"bells.cs.u.694:07.01.91.15.48.34"@cs.ucl.ac.uk>
X400-Content-Identifier: Greetings. |
MIME-Version: 1.0 |
Content-Type: multipart/report; report-type=delivery-status; |
boundary=boundary-1 |

--boundary-1 |

This report relates to your message: Greetings. *

of Thu, 7 Feb 1991 15:48:20 +0000 |

Your message was not delivered to
H.Hildegard@bbn.com for the following reason:
Bad Address
MTA 'bbn.com' gives error message (USER) Unknown user name in
"H.Hildegard@bbn.com"

The Original Message follows: |

--boundary-1 ||
content-type: message/delivery-status ||

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Reporting-MTA: x400; bells.cs.ucl.ac.uk in /PRMD=uk.ac/ADMD=gold 400/C=gb/|| 400/C=gb/
Arrival-Date: Thu, 7 Feb 1991 15:48:34 +0000 ||
DSN-Gateway: dns; bells.cs.ucl.ac.uk ||
X400-Conversion-Date: Thu, 7 Feb 1991 15:48:40 +0000 ||
Original-Envelope-Id: ||
[/PRMD=uk.ac/ADMD=gold 400/C=gb/;<1803.665941698@UK.AC.UCL.CS>]|| 400/C=gb/;<1803.665941698@UK.AC.UCL.CS>]
X400-Content-Identifier: Greetings. ||
X400-Subject-Intermediate-Trace-Information: /PRMD=uk.ac/ADMD=gold 400/C=gb/;|| 400/C=gb/;
arrival Thu, 7 Feb 1991 15:48:20 +0000 action Relayed ||
X400-Subject-Intermediate-Trace-Information: /PRMD=uk.ac/ADMD=gold 400/C=gb/;|| 400/C=gb/;
arrival Thu, 7 Feb 1991 15:48:18 +0000 action Relayed ||

Original-Recipient: rfc822; H.Hildegard@bbn.com ||
Final-Recipient: x400; ||
/RFC-822=H.Hildegard(a)bbn.com/OU=cs/O=ucl/PRMD=uk.ac/ADMD=gold 400/C=gb/;|| 400/C=gb/;
Action: failure ||
Status: 5.1.1 ||
Diagnostic Code: x400; Reason Unable-To-Transfer (1); ||
Diagnostic Unrecognised-ORName (0) ||
X400-Last-Trace: (ia5) Thu, 7 Feb 1991 15:48:18 +0000; ||
X400-Originally-Specified-Recipient-Number: 1 ||
X400-Supplementary-Info: "MTA 'bbn.com' gives error message (USER)|| (USER)
Unknown user name in "H.Hildegard@bbn.com""; ||

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--boundary-1 |
Content-Type: message/rfc822 |

Received: from glenlivet.cs.ucl.ac.uk by bells.cs.ucl.ac.uk
with SMTP inbound id <27689-0@bells.cs.ucl.ac.uk>;
Thu, 7 Feb 1991 15:48:21 +0000
To: H.Hildegard@bbn.com
Subject: Greetings.
Phone: +44-71-380-7294
Date: Thu, 07 Feb 91 15:48:18 +0000
Message-ID: <1803.665941698@UK.AC.UCL.CS>
From: Steve Kille <S.Kille@cs.ucl.ac.uk>

Steve

--boundary-1

--boundary-1-- |

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Example Delivery Report 2:

Received: from cs.ucl.ac.uk by bells.cs.ucl.ac.uk *
via Delivery Reports Channel id <27718-0@bells.cs.ucl.ac.uk>;
Thu, 7 Feb 1991 15:49:11 +0000
X400-Received: by mta bells.cs.ucl.ac.uk in /PRMD=uk.ac/ADMD=gold 400/C=gb/;
Relayed; Thu, 7 Feb 1991 15:49:08 +0000
X400-Received: by /PRMD=DGC/ADMD=GOLD 400/C=GB/; Relayed;
Thu, 7 Feb 1991 15:48:40 +0000
From: UCL-CS MTA <postmaster@cs.ucl.ac.uk>
To: S.Kille@cs.ucl.ac.uk
Subject: Delivery Report (failure) for
j.nosuchuser@dle.cambridge.DGC.gold-400.gb
Message-Type: Delivery Report
Date: Thu, 7 Feb 1991 15:46:11 +0000 |
Message-ID: <"DLE/910207154840Z/000"@cs.ucl.ac.uk>
X400-Content-Identifier: A useful mess... |
MIME-Version: 1.0 |
Content-Type: multipart/report; report-type=delivery-status; |
boundary=boundary-1 |

--boundary-1 |

This report relates to your message: A useful mess...

of Thu, 7 Feb 1991 15:43:20 +0000 |

Your message was not delivered to
j.nosuchuser@dle.cambridge.DGC.gold-400.gb
for the following reason:
Bad Address
DG 21187: (CEO POA) Unknown addressee.

The Original Message is not available |

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--boundary-1 |
content-type: message/delivery-status |

Reporting-MTA: x400; /PRMD=DGC/ADMD=GOLD 400/C=GB/ |
Arrival-Date: Thu, 7 Feb 1991 15:48:40 +0000 |
DSN-Gateway: dns; bells.cs.ucl.ac.uk |
X400-Conversion-Date: Thu, 7 Feb 1991 15:49:12 +0000 |
Original-Envelope-Id: |
[/PRMD=uk.ac/ADMD=gold 400/C=gb/;<1796.665941626@UK.AC.UCL.CS>] |
X400-Content-Identifier: A useful mess... |

Original-Recipient: rfc822; j.nosuchuser@dle.cambridge.DGC.gold-400.gb
Final-Recipient: x400;
/I=j/S=nosuchuser/OU=dle/O=cambridge/PRMD=DGC/ADMD=GOLD 400/C=GB/
Action: failure
Status: 5.1.1
Diagnostic Code: x400; Reason Unable-To-Transfer (1);
Diagnostic Unrecognised-ORName (0)
X400-Supplementary-Info: "DG 21187: (CEO POA) Unknown addressee."
X400-Originally-Specified-Recipient-Number: 1

--boundary-1

--boundary-1-- |

5.3.9. Probe |

This is an MTS internal issue. Any probe shall be serviced by
the gateway, as there is no equivalent RFC 822 functionality.
The value of the reply is dependent on whether the gateway could
service an MTS Message with the values specified in the probe.
The reply shall make use of MTS.SupplementaryInformation to
indicate that the probe was serviced by the gateway.

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Appendix A - Mappings Specific to SMTP

This Appendix is specific to the Simple Mail Transfer Protocol
(RFC 821). It describes specific changes in the context of this |
protocol. When MIXER is used with SMTP, conformance to this |
appendix is mandatory.

6. Probes |

When servicing a probe, as described in section 5.3.9, use may be
made of the SMTP VRFY command to increase the accuracy of
information contained in the delivery report. |

7. Long Lines |

SMTP is a text oriented protocol, and is required to support a |
line length of at least 1000 characters. Some implementations |
do not support line lengths greater than 1000 characters. This |
can cause problems. Where body parts have long lines, it is |
recommended to use a MIME encoding that folds lines (quoted |
printable). |

8. SMTP Extensions |

There are several RFCs that specify extensions to SMTP. Most of |
these are not relevant to MIXER. The NOTARY work to support |
delivery report defines extensions which are relevant [34]. [30]. Use |
of these extensions by a MIXER gateway is optional. If these |
extensions are used, they shall be used in the manner described |
below. |

Editor's Note: |
It has been proposed to make these extensions mandatory. |
Input is solicited.

8.1. SMTP Extension mapping to X.400 |

Mappings are defined for the following extensions:

NOTIFY |

NOTIFYThis
This is used to set the report and non-delivery bits of |
MTS.MTS.PerRecipientMessageSubmissionFields.originator-report-request.|
MTS.MTS.PerRecipientMessageSubmissionFields.originator-report-request.
If the value is NEVER, both bits are zero. If SUCCESS is |
present, the report bit is set. Otherwise, the non- |

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delivery-report bit is set. If the gateway uses the NOTIFY |
command, it shall perform this mapping in all cases.

ORCPT |

ORCPTThis
This may be used at the MTS level, to generate an element of |
redirection history, with the redirection date being the |
date of conversion. |

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8.2. X.400 Mapping to SMTP Extensions |

The following extensions may be used as a part of the MIXER |
mapping:

NOTIFY |

NOTIFYThe
The report and non-delivery bits of |
MTS.MTS.PerRecipientMessageSubmissionFields.originator-report-request|
MTS.MTS.PerRecipientMessageSubmissionFields.originator-report-request
determine how this is used. If both bits are zero, the |
parameter is NEVER. If the report bit is set, SUCCESS is |
used. Otherwise, FAILURE is used. If this is done, the |
gateway shall not generate a delivery report for this |
recipient.

ORCPT |

ORCPTIf
If the |
MTS.perRecipientReportDeliveryFields.originally-intended-recipient-name|
MTS.perRecipientReportDeliveryFields.originally-intended-recipient-name
is present, the ORCPT command may be used to carry this |
value.

ENVID |

ENVIDThis
This may be generated, with the value taken from the |
MTS.MessgeDeliveryEnvelope.message-delivery-identifer, |
encoded as EBNF.mts-msg-id.

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Appendix B - Mapping with X.400(1984) |

This appendix defines modification modifications to the mapping for use with |
X.400(1984).

The X.400(1984) protocols are a proper subset of |
X.400(1988). When mapping from X.400(1984) to RFC 822, no |
changes to this specification are needed.

When mapping from RFC 822 to X.400(1984), no use can be made |
of 1988 specific features. No use of such features is made at |
the MTS level. One feature is used at the IPMS level, and this |
must be replaced by the RFC 987 approach. All header information |
which would usually be mapped into the rfc-822-heading-list |
extension, together with any Comments: field in the RFC 822 |
header
extension is mapped into a single IA5 body part, which is the first |
first body part in the message. This body part will start with
the | string "RFC-822-Headers:" as the first line. The headers
then | follow this line. This specification requires correct
reverse | mapping of this format, either from 1988 or 1984. RFC
822 | extended headers which could be mapped into X.400(1988)
elements, | are also mapped to the body part.

In an environment where RFC 822 is of major importance, it |
may be desirable for downgrading to consider the case where the |
message was originated in an RFC 822 system, and mapped according |
to this specification. The rfc-822-heading-list extension may be |
mapped according to this appendix. |

When parsing std-or, the following restrictions must be |
observed: |

- Only the 84/88 attributes identified in the table in |
Section 4.2 are present. |

- No teletex encoding is allowed.

If an address violates this, it should be treated as an RFC 822 |
address, which will usually lead to encoding as a DDA "RFC-822". |

It is possible that null attributes may be present in an O/R |
Address. This is not legal in 1988, except for ADMD where the |
case is explicitly described in Section 4.3.5. Null attributes |

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are deprecated (the attribute should be omitted), and should |

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therefore be unusual. However, some systems generate them and |
rely on them. Therefore, any null attribute shall be enoded |
using the std-or encoding (e.g., /O=/). |

If a non-Teletex Common Name (CN) is present, it should be |
mapped onto a Domain Defined Attribute "Common". This is in line |
with RFC 1328 on X.400 1988 to 1984 downgrading . | [23].

This specification defines a mapping of the Internet message |
framework to X.400. Body part mappings are defined in RFC 1494 |
[12],
1494bis , which relies on X.400(88) features. Downgrading to | [
X.400(84) for body parts is defined in RFC 1496 (HARPOON), which | [
shall be followed in the context of this appendix [11]. [6]. [

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Appendix C - RFC 822 Extensions for X.400 access | [

This appendix defines a number of optional mappings which may be | [
provided to give access from RFC 822 to a number of X.400 | [
services. These mappings are beyond the basic scope of this | [
specification. There has been a definite demand to use extended | [
RFC 822 as a mechanism to access X.400, and these extensions | [
provide access to certain features. If this functionality is | [
provided, this appendix shall be followed. The following | [
headings are defined: | [

extended-heading =
"Prevent-NonDelivery-Report" ":"
/ "Generate-Delivery-Report" ":"
/ "Alternate-Recipient" ":" prohibition
/ "Disclose-Recipients" ":" prohibition
/ "Content-Return" ":" prohibition

Prevent-NonDelivery-Report and Generate-Delivery-Report allow | [
setting of | [
MTS.PerRecipientSubmissionFields.originator-report-request. The | [
setting will be the same for all recipients. | [

Alternate-Recipient, Disclose-Recipients, and Content-Return | [
allow for override of the default settings for | [
MTS.PerMessageIndicators. [

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Appendix D - Object Identifier Assignment [

The following Object Identifiers shall be used. [

internet ::= OBJECT IDENTIFIER { iso org(3) dod(6) 1 } -- from RFC 1155|
|
mail OBJECT IDENTIFIER ::= { internet 7 } -- IANA assigned |

mixer OBJECT IDENTIFIER ::= {iso(1) org(3) dod(6) internet(1) { mail mixer(1) } -- inherited from RFC 1495|
mixer-headings OBJECT IDENTIFIER ::= { mixer headings(1) } |
private(4) enterprises(1) isode-consortium (453)
mixer-bodies OBJECT IDENTIFIER ::= { mixer bodies(2) } |
mixer(15)}
|
id-rfc-822-field-list OBJECT IDENTIFIER ::= {mixer field(1)} {mixer-headings 3} |
id-hex-multipart-message OBJECT IDENTIFIER ::= {mixer field(2)} {mixer-headings 4} |
id-hex-partial-message OBJECT IDENTIFIER ::= {mixer field(3)} {mixer-headings 1} |
id-dsn-header-list OBJECT IDENTIFIER ::= {mixer field(4)} {mixer-headings 5} |
id-dsn-field-list OBJECT IDENTIFIER ::= {mixer field(5)} {mixer-headings 6} |
id-mime-body-part OBJECT IDENTIFIER ::= {mixer field(6)} {mixer-bodies 1} |
id-mime-body-part-parameters OBJECT IDENTIFIER ::= {mixer field(7)}| {mixer-bodies 2}|

This object identifier for id-rfc-822-field-list is different to | [
the one assigned in RFC 1327, which was erroneous. |

Editor's |
ISO has been asked for an Object Identifier root, which is |
expected to replace this one. The above ID is a (valid) |
place-holder, in case this assignment does not materialise. *

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Appendix E - BNF Summary

boolean = "TRUE" / "FALSE"

numericstring = *DIGIT

printablestring = *( ps-char )
ps-restricted-char = 1DIGIT / 1ALPHA / " " / "'" / "+"
/ "," / "-" / "." / "/" / ":" / "=" / "?"
ps-delim = "(" / ")"
ps-char = ps-delim / ps-restricted-char

ps-encoded = *( ps-restricted-char / ps-encoded-char )
ps-encoded-char = "(a)" ; (@)
/ "(p)" ; (%)
/ "(b)" ; (!)
/ "(q)" ; (")
/ "(u)" ; (_)
/ "(l)" ; "("
/ "(r)" ; ")"
/ "(" 3DIGIT ")"

teletex-string = *( ps-char / t61-encoded )
t61-encoded = "{" 1* t61-encoded-char "}"
t61-encoded-char = 3DIGIT

teletex-and-or-ps = [ printablestring ] [ "*" teletex-string ]

labelled-integer ::= [ key-string ] "(" numericstring ")"

key-string = *key-char
key-char = <a-z, A-Z, 0-9, and "-">

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object-identifier ::= oid-comp object-identifier
| oid-comp

oid-comp ::= [ key-string ] "(" numericstring ")"

encoded-info = 1#encoded-type

encoded-type = built-in-eit / object-identifier

encoded-pn = [ given "." ] *( initial "." ) surname

given = 2*<ps-char not including ".">

initial = ALPHA

surname = printablestring

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standard-type = key-string

registered-dd-type
= key-string dd-key = key-string

value = std-printablestring

std-printablestring
= *( std-char / std-pair ) std-char
= <"{", "}", "*", and any ps-char |
except "/" and "="> "=" >
std-pair = "$" ps-char

global-id = std-or-address *

mta-field = "X400-Received" ":" x400-trace
/ "Deferred-Delivery" ":" date-time
/ "Latest-Delivery-Time" ":" date-time

x400-trace = "by" md-and-mta ";"
[ "deferred until" date-time ";" ]
[ "converted" "(" encoded-info ")" ";" ]
[ "attempted" md-or-mta ";" ]
action-list
";" arrival-time

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md-and-mta = [ "mta" mta "in" ] global-id
mta = word
arrival-time = date-time

md-or-mta = "MD" global-id
/ "MTA" mta

Action-list = 1#action
action = "Redirected"
/ "Expanded"
/ "Relayed"
/ "Rerouted"

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dr-user-info = dr-summary <CRLF> |
dr-recipients <CRLF>
dr-content-return *

dr-content-return = "The Original Message is not available"
/ "The Original Message follows:"

dr-summary = "This report relates to your message:" <CRLF>
content-correlator <CRLF> <CRLF>
"of" date-time <CRLF> <CRLF>

dr-recipients = *(dr-recipient <CRLF> <CRLF>)

dr-recipient = dr-recip-success / dr-recip-failure

dr-recip-success =
"Your message was successfully delivered to:"
mailbox "at" date-time

dr-recip-failure = "Your message was not delivered to:"
mailbox <CRLF>
"for the following reason:" *word

report-point = [ "mta" word "in" ] global-id |
content-correlator = *word |

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dr-extensions = "X400-Discarded-DR-Extensions" ":" |
1# (object-identifier / labelled-integer)| labelled-integer)

dl-history = 1#( mailbox "(" date-time ")") |

/ "X400-Diagnostic" ":" labelled-integer |
/ "X400-Reason" ":" labelled-integer |

dr-diagnostic = "Reason" labelled-integer |
[ ";" "Diagnostic" labelled-integer ] |

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prohibition = "Prohibited" / "Allowed"

mts-msg-id = "[" global-id ";" *text "]"

mts-content-type = "P2" / labelled-integer
/ object-identifier |

priority = "normal" / "non-urgent" / "urgent"

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ipn-body-format = ipn-description <CRLF> *
[ ipn-extra-information <CRLF> ]
[ ipn-content-return ]

ipn-description = ipn-receipt / ipn-non-receipt

ipn-non-receipt "Your message to:"
preferred-recipient <CRLF>
ipn-reason

ipn-reason = ipn-discarded / ipn-auto-forwarded

ipn-discarded = "was discarded for the following reason:"
discard-reason <CRLF>

ipn-auto-forwarded = "was automatically forwarded." <CRLF>
[ "The following comment was made:"
auto-comment ]

ipn-extra-information =
"The following information types were converted:"
encoded-info

ipn-content-return = "The Original Message is not available"
/ "The Original Message follows:"

preferred-recipient = mailbox
receipt-time = date-time
auto-comment = printablestring
ipn-suppl = printablestring

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discard-reason = "Expired" / "Obsoleted" /
"User Subscription Terminated"

acknowledgement-mode = "Manually" / "Automatically"

importance = "low" / "normal" / "high"

sensitivity = "Personal" / "Private" /
"Company-Confidential"

language = 2*ALPHA [ language-description ]
language-description = printable-string

message-type = "Delivery Report" |
/ "InterPersonal Notification"
/ "Multiple Part"

autosubmitted = "not-auto-submitted" ||
/ "auto-generated" ||
/ "auto-replied" ||
/ "auto-forwarded" ||

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redirect-comment =
[ "Originally To:" ] mailbox "Redirected"
[ "Again" ] "on" date-time
"To:" redirection-reason

subject-line = "Delivery-Report" "(" status ")"
[ "for" destination ]

status = "success" / "failure" / "success and failures"

destination = mailbox / "MTA" word

extended-heading =
"Prevent-NonDelivery-Report" ":"
/ "Generate-Delivery-Report" ":"
/ "Alternate-Recipient" ":" prohibition
/ "Disclose-Recipients" ":" prohibition
/ "Content-Return" ":" prohibition

ftbp-field = "FTBP-Pathname" ":" *text
/ "FTBP-Object-Size" ":" integer |
/ "FTBP-Creation-Date" ":" date-time
/ "FTBP-Modification-Date" ":" date-time
"FTBP-Read-Date" ":" date-time

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Appendix F - Format of address mapping tables |

1. Global Mapping Information

The consistent operation of gateways which follow this
specification relies of the existence of three globally defined
mappings:

1. Domain Name Space -> O/R Address Space

2. O/R Address Space -> Domain Name Space

3. Domain Name Space -> O/R Address of preferred gateway

All gateways conforming to this specification shall have access |
to and use these mappings. The gateway may use standardised or
private mechanisms to access this mapping information.

One means of distributing this information is in three
files. This appendix defines a format for these files. |

2. Mechanisms to register and to distribute Mapping Rules |

To get a contact address of the mapping registration |
authority for the |
respective country or more information about the MailFLOW |

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Project |
contact: |

email: mailflow@mailflow.dante.net ||
S=MailFLOW;O=MailFLOW;P=DANTE;A=mailnet;C=fi; ||

fax: +41 1 268 15 68 ||
tel: +41 1 268 15 20 ||

3. Syntax Definitions

An address syntax is defined, which is compatible with the syntax
used for 822.domains. By representing the O/R addresses as
domains, all lookups can be mechanically implemented as domain ->
domain mappings. This syntax defined is initially for use in
table format, but the syntax is defined in a manner which makes
it suitable to be adapted for use with the Domain Name Service.
This syntax allows for a general representation of O/R addresses,
so that it can be used in other applications. Not all attributes
are used in the table formats defined.

To allow the mapping of null attributes to be represented,
the pseudo-value "@" (not a printable string character) is used
to indicate omission of a level in the hierarchy. This is
distinct from the form including the element with no value,
although a correct X.400 implementation will interpret both in
the same manner.

This syntax is not intended to be handled by users.

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dmn-or-address = dmn-part *( "." dmn-part ) |
mn-part = dmn-attribute "$" value |
dmn-attribute = standard-type |
/ "~" dmn-printablestring |
value = dmn-printablestring
/ "@"
dmn-printablestring =
= *( dmn-char / dmn-pair )
dmn-char = <"{", "}", "*", and any ps-char
except ".">
dmn-pair = "\."

An example usage:

~ROLE$Big\.Chief.ADMD$ATT.C$US
PRMD$DEC.ADMD$@.C$US

The first example illustrates quoting of a "." and a domain |
define attribute (ROLE). The second example illustrates |
omission of the ADMD level. There must be a strict ordering of
all components in this table, with the most significant
components on the RHS. This allows the encoding to be treated
as a domain.

Various further restrictions are placed on the usage of
dmn-or-address in the address space mapping tables.

1. Only C, ADMD, PRMD, O, and up to four OUs may be used.

2. No components shall be omitted from this hierarchy, although
the hierarchy may terminate at any level. If the mapping is
to an omitted component, the "@" syntax is used.

4. Table Lookups

When determining a match, there are aspects which apply to all
lookups. Matches are always case independent. The key for all
three tables is a domain. The longest possible match shall be
obtained. Suppose the table has two entries with the following
keys:

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K.L
J.K.L

Domain "A.B.C" will not return any matches. Domain "I.J.K.L"
will match the entry "J.K.L:.

5. Domain -> O/R Address format

The BNF is:

domain-syntax "#" dmn-or-address "#"

EBNF.domain-syntax is defined in Section 4.2. Note that the |
trailing "#" is used for clarity, as the dmn-or-address syntax |
might lead to values with trailing blanks. Lines starting with |
"#" are comments.

For example:
AC.UK#PRMD$UK\.AC.ADMD$GOLD 400.C$GB#
XEROX.COM#O$Xerox.ADMD$ATT.C$US#
GMD.DE#O$@.PRMD$GMD.ADMD$DBP.C$DE#

A domain is looked up to determine the top levels of an O/R
Address. Components of the domain which are not matched are used
to build the remainder of the O/R address, as described in
Section 4.3.4.

6. O/R Address -> Domain format

The syntax of this table is:

dmn-or-address "#" domain-syntax "#"

For example:

#
# Mapping table
#
PRMD$UK\.AC.ADMD$GOLD 400.C$GB#AC.UK#

The O/R Address is used to generate a domain key. It is
important to order the components correctly, and to fill in

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missing components in the hierarchy. Use of this mapping is
described in Section 4.3.2.

7. Domain -> O/R Address of Gateway table

This uses the same format as the domain -> O/R address mapping. |
In this case, the restriction to only use C/ADMD/PRMD/O/OU does |
not apply. Use of this mapping is described in Section 4.3.4. A |
domain cannot appear in this table and in the domain to O/R |
Address table.

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Appendix G - Conformance |

This appendix defines a number of options, which a conforming *
gateway should specify. Conformance to this specification shall
not be claimed if any of the mandatory features are not |
implemented. A specification of conformance may list the service |
elements of Chapter 2, in order to be clear that full conformance |
is provied. In particular:

- Formats for all fields shall be followed.

- The global mappings shall be supported. |

- Formats for subject lines, delivery reports and IPNs shall
be followed. A system which followed the syntax, but
translated text into a language other than english would be
conformant.

- RFC 1137 shall not be followed when mapping to SMTP. |

- All mappings of trace shall be implemented.

- There must be a mechanism to access all three global
mappings. |

- RFC 1494 1494bis shall be followed for mapping body parts. |

- When it is specified that a MIME format message is |
generated, RFC 1521 shall be followed.

A gateway should specify:

- Which 822-MTS Interent Message Transport (822-MTS) protocols are |
supported. If SMTP is | supported, Appendex A of MIXER shall
be used.

- Which X.400 versions are supported (84, 88, 92). |

- The means by which it can access the global mappings.
Currently, the tables of the formats define in Appendix F
is the only means available.

- The approach taken to return of contents (5.2) *

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- The approach taken to multiple copies vs non-disclosure *
(4.6.2.2) |

- The mechanism or mechanisms by which the global mapping | *

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information is accessed.

The following are optional parts of this specification. A
conforming implementation should specify which of these it
supports.

- Generation of extended RFC 822 fields is mandatory.
Optionally, they may be parsed and mapped back to X.400. A
gateway should should indicate if this is done, listing the |
mappings performed according to each service element of |
Chapter 2.

- Support for the extension mappings of Appendix C. |

- Support for returning illegal format content in a delivery
report

- Which address interpretation heuristics are supported
(4.3.4.1)

- If RFC 987 generated message ids are handled in a backwards
compatible manner (4.7.3.6) |

- Support for FTBP.

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Appendix H - Change History: RFC 987, 1026, 1138, 1148 |

RFC 987 was the original document, and contained the key elements
of this specification. It was specific to X.400(1984). RFC 1026
specified a small number of necessary changes to RFC 987.

RFC 1138 was based on the RFC 987 work. It contained an
editorial error, and was reissued a few months later as RFC 1148.
RFC 1148 will be referred to here, as it is the document which is
widely referred to elsewhere. The major goal of RFC 1148 was to
upgrade RFC 987 to X.400(1988). It did this, but did not
obsolete RFC 987, which was recommended for use with X.400(1984).
This appendix summarises the changes made in going from RFC 987
to RFC 1148.

RFC 1148 noted the following about its upgrade from RFC 987:
Unnecessary change is usually a bad idea. Changes on the RFC 822
side are avoided as far as possible, so that RFC 822 users do
not see arbitrary differences between systems conforming to this
specification, and those following RFC 987. Changes on the X.400
side are minimised, but are more acceptable, due to the mapping
onto a new set of services and protocols.

1. Introduction

The model has shifted from a protocol based mapping to a service
based mapping. This has increased the generality of the
specification, and improved the model. This change affects the
entire document.

A restriction on scope has been added.

2. Service Elements

- The new service elements of X.400 are dealt with.

- A clear distinction is made between origination and
reception

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3. Basic Mappings

- Add teletex support

- Add object identifier support

- Add labelled integer support

- Make PrintableString <-> ASCII mapping reversible

- The printable string mapping is aligned to the NBS mapping
derived from RFC 987.

4. Addressing

- Support for new addressing attributes

- The message ID mapping is changed to not be table driven

5. Detailed Mappings

- Define extended IPM Header, and use instead of second body
part for RFC 822 extensions

- Realignment of element names

- New syntax for reports, simplifying the header and
introducing a mandatory body format (the RFC 987 header
format was unusable)

- Drop complex autoforwarded mapping

- Add full mapping for IP Notifications, defining a body
format

- Adopt an MTS Identifier syntax in line with the O/R Address
syntax

- A new format for X400 Trace representation on the RFC 822
side

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6. Appendices

- Move Appendix on restricted 822 mappings to a separate RFC

- Delete Phonenet and SMTP Appendixes

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Appendix I - Change History: RFC 1148 to RFC 1327 |

1. General

- The scope of the document was changed to cover X.400(1984),
and so obsolete RFC 987.

- Changes were made to allow usage to connect RFC 822 networks
using X.400

- Text was tightened to be clear about optional and mandatory
aspects

- A good deal of clarification

- A number of minor EBNF errors

- Better examples are given

- Further X.400 upper bounds are handled correctly

2. Basic Mappings

- The encoding of object identifier is changed slightly

3. Addressing

- A global mapping of domain to preferred gateway is
introduced.

- An overflow mechanism is defined for RFC 822 addresses of
greater than 128 bytes

- Changes were made to improve compatibility with the PDAM on |
writing O/R Addresses.

+ The PD and Terminal Type keywords were aligned to the
PDAM. It is believed that minimal use has been made of
the RFC 1148 keywords.

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+ P and A are allowed as alternate keys for PRMD and ADMD

+ Where keywords are different, the PDAM keywords are
alternatives on input. This is mandatory.

4. Detailed Mappings

- The format of the Subject: lines is defined.

- Illegal use (repetition) of the heading EXTENSION is
corrected, and a new object identifier assigned.

- The Delivery Report format is extensively revised in light
of operational experience.

- The handling of redirects is significantly changed, as the
previous mechanism did not work.

5. Appendices

- An SMTP appendix is added, allowing optional use of the VRFY
command to improve probe information.

- Handling of JNT Mail Acknowledge-To is changed slightly.

- A DDA JNT-MAIL is allowed on input.

- The format definitions of Appendix F are explained further,
and a third table definition added.

- An appendix on use with X.400(1984) is added.

- Optional extensions are defined to give RFC 822 access to
further X.400 facilities.

- An appendix on conformance is added. |

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Appendix J - Change History: RFC 1327 to this Document |

1. General |

This update is primarily for stability, and to fold in |
compatibility for MIME and to add support for the new NOTARY |
delivery status notifications. Other general changes: |

- Various editorial updates |

- Minor EBNF errors |

- Reference to mapping table support by DNS and X.500. |

- Alignment to X.400(92) |

- Assignment of a new object identifier |

- Support for the EMA profile of the File Transfer Body Part. |

2. Service Elements |

- Support of Auto-Submitted service |

3. Basic Mappings |

- Comments may not be used in new headers, to remove parsing |
ambiguity |

- RFC 1522 encoding may be used as an alternative to X.408 |
downgrade, where appropriate. |

4. Addressing |

- Restructure of text to emphasise the global mappings |

- Add codes and add a heuristic to align to the standard X.400 |
form of writing O/R Addresses. |

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- Improved text on ordering heuristic |

- Leading "/" heuristic interpretation added |

- All bar one of the address mapping heuristics made |
mandatory. |

- Interpretation of domain defined attribute "RFC-822" made |
mandatory in all cases |

- Make report request comments optional |

5. Detailed Mappings |

- Comments no loner longer maps to separate body part |

- Allow Langauges to be multi-valued |

- Change Content-Identifier to X400-Content-Identifier, in |
order to avoid confusion with MIME. |

- Reverse mapping of MIXER defined fields made mandatory

6. Appendices |

- Relaxation of restrictions on mapping 3 in Appendix F. |

- Add linkage to HARPOON in Appendix B. |

- RFC 1494 1494bis added to the conformance statement of Appendix G. |
G.

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SECURITY CONSIDERATIONS

Security considerations are not discussed in this RFC.

AUTHOR'S ADDRESS

Phone: +44-181-332-9091 |

Internet EMail: S.Kille@ISODE.COM |

X.400 Email: I=S; S=Kille; O=ISODE Consortium; P=ISODE; A=Mailnet; C=FI;| C=FI;

UFN: S.Kille, ISODE Consortium, GB |

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References

2. CCITT SG 5/VII, "Recommendations X.400," Message Handling
Systems: System Model - Service Elements, October 1984.

8. C. Allocchio, "Mapping between X.400(1984/1988) and Mail-11
(DECnet mail)," RFC 1405, jan 1993.

4. C. Allocchio, B. Cole, S. Giordano, and R. Hagens, "Using
the Internet DNS to Distribute RFC 1327 Mail Address Mapping
Tables," RFC 1664, aug 1994.

10.

5. H.T. Alvestrand, S.E. Kille, R. Miles, M. Rose, and S.
Thompson, "Mapping between X.400 and RFC-822 Message
Bodies," RFC 1495, Aug 1993.

11.

6. H.T. Alvestrand, J. Romaguera, and K. Jordan, "Rules for
Downgrading Messages for X.400(88) to X.400(84) When MIME
Consent-Types are Present in the Messages (Harpoon)," RFC
1496, Aug 1993.

12.

7. H.T. Alvestrand and S. Thompson, "Equivalences between X.400
and RFC-822 Message Bodies," RFC 1494, Aug 1993.

13.

8. H.T. Alvestrand, "Tags for the Identification of Languages,"
RFC 17566, March 1995.

14.

9. N. Borenstein and N. Freed, "MIME (Multipurpose Internet
Mail Extensions)," RFC 1521, Sep 1993.

15.

10. R.T. Braden, "Requirements for Internet Hosts -- Application
and Support," RFC 1123, Oct 1989.

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16.

11. CCITT/ISO, "CCITT Recommendations X.420/ ISO IS 10021-7,"
Message Handling Systems: Interpersonal Messaging System,
December 1988.

17.

12. CCITT/ISO, "CCITT Recommendations X.411/ ISO IS 10021-4,"
Message Handling Systems: Message Transfer System: Abstract
Service Definition and Procedures, December 1988.

18.

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13. CCITT/ISO, "CCITT Recommendations X.400/ ISO IS 10021-1,"
Message Handling: System and Service Overview , December
1988.

14. CCITT/ISO, "Specification of Abstract Syntax Notation One
(ASN.1)," CCITT Recommendation X.208 / ISO IS 8824, December
1988.

19. CCITT/ISO, "CCITT Recommendations X.400/ ISO IS 10021-1,"
Message Handling: System and Service Overview , December
1988.

20.

15. CCITT/ISO, "CCITT Recommendations X.400/ ISO IS 10021-1,"
Message Handling: System and Service Overview , December
1992.

21.

16. D.H. Crocker, "Standard of the Format of ARPA Internet Text
Messages," RFC 822, August 1982.

22.

17. S.E. Kille, "Mapping Between X.400 and RFC 822," UK Academic
Community Report (MG.19) / RFC 987, June 1986.

23.

18. S.E. Kille, "Addendum to RFC 987," UK Academic Community
Report (MG.23) / RFC 1026, August 1987.

24.

19. S.E. Kille, "Mapping between full RFC 822 and RFC 822 with
restricted encoding," RFC 1137, October 1989.

25.

20. S.E. Kille, "Mapping Between X.400(1988) / ISO 10021 and RFC
822," RFC 1138, October 1989.

26.

21. S.E. Kille, "Mapping Between X.400(1988) / ISO 10021 and RFC
822," RFC 1148, March 1990.

27.

22. S.E. Kille, "Mapping Between X.400(1988) / ISO 10021 and RFC
822," RFC 1327, May 1992.

28.

23. S.E. Kille, "X.400 1988 to 1984 downgrading," RFC 1328, May
1992.

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29.

24. S.E. Kille, "A String Encoding of Presentation Address," RFC
1278, Nov 1992.

25. S.E. Kille, "A String Representation of Distinguished Name,"
RFC 1485, Jan 1992.

30.

26. S.E. Kille, "Using the OSI Directory to achieve User
Friendly Naming," RFC 1484, Jan 1992.

31.

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27. S.E. Kille, "Use of the X.500 Directory to support mapping
between X.400 and RFC 822 Addresses," RFC in preparation,
Sep 1994.

32.

28. N. Koorland, "Message Attachmment Work Group (MAWG): MAWG
Feasibility Project Guide," EMA Report, Version 1.3, March
1995.

33.

29. K. Moore and G. Vaudreuil, "An Extensible Message Format for
Delivery Status Notifications," RFC Draft, May 1995.

34.

30. K. Moore, "SMTP Service Extensions for Delivery Status
Notifications," RFC Draft, May 1995.

35.

31. J.B. Postel, "SIMPLE MAIL TRANSFER PROTOCOL," RFC 821,
August 1982.

36.

32. CEN/CENELEC/Information Technology/Working Group on Private
Message Handling Systems, "FUNCTIONAL STANDARD A/3222,"
CEN/CLC/IT/WG/PMHS N 17, October 1985.

33. R. Troot and S. Dorner, "Communicating Presentation
Information in Internet Messages: The Content Dispostion
Header," RFC 1806, June 1995.

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1 - General ....................................... 166
2 - Basic Mappings ................................ 166
3 - Addressing .................................... 166
4 - Detailed Mappings ............................. 167
5 - Appendices .................................... 167
Appendix J - Change History: RFC 1327 to this Document |
168......................................................... |
............................................................ 168
1 - General 168.................................... | ....................................... 168
2 - Service Elements 168........................... | .............................. 168
3 - Basic Mappings 168............................. | ................................ 168
4 - Addressing 168................................. | .................................... 168
5 - Detailed Mappings 169.......................... |
6 - Appendices 169................................. | ............................. 169

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6 - Appendices .................................... 169

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----