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rfc:rfc1327

Network Working Group S. Hardcastle-Kille Request for Comments: 1327 University College London Obsoletes: RFCs 987, 1026, 1138, 1148 May 1992 Updates: RFC 822

        Mapping between X.400(1988) / ISO 10021 and RFC 822

Status of this Memo

 This RFC specifies an IAB standards track protocol for the Internet
 community, and requests discussion and suggestions for improvements.
 Please refer to the current edition of the "IAB Official Protocol
 Standards" for the standardization state and status of this protocol.
 Distribution of this memo is unlimited.

Abstract

 This document describes a set of mappings which will enable
 interworking between systems operating the CCITT X.400 1988)
 Recommendations on Message Handling Systems / ISO IEC 10021 Message
 Oriented Text Interchange Systems (MOTIS) [CCITT/ISO88a], and systems
 using the RFC 822 mail protocol [Crocker82a] or protocols derived
 from RFC 822.  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 RFCs 987, 1026, 1138, and 1148
 [Kille86a,Kille87a] which it obsoletes.
 This document specifies a mapping between two protocols.  This
 specification should be used when this mapping is performed on the
 DARPA Internet or in the UK Academic Community.  This specification
 may be modified in the light of implementation experience, but no
 substantial changes are expected.

Table of Contents

 1          - Overview ......................................    3
 1.1        - X.400 .........................................    3
 1.2        - RFC 822 .......................................    3
 1.3        - The need for conversion .......................    4
 1.4        - General approach ..............................    4
 1.5        - Gatewaying Model ..............................    5
 1.6        - X.400 (1984) ..................................    8
 1.7        - Compatibility with previous versions ..........    8
 1.8        - Aspects not covered ...........................    8
 1.9        - Subsetting ....................................    9
 1.10       - Document Structure ............................    9

Hardcastle-Kille [Page 1] RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992

 1.11       - Acknowledgements ..............................    9
 2          - Service Elements ..............................   10
 2.1        - The Notion of Service Across a Gateway ........   10
 2.2        - RFC 822 .......................................   11
 2.3        - X.400 .........................................   15
 3          - Basic Mappings ................................   24
 3.1        - Notation ......................................   24
 3.2        - ASCII and IA5 .................................   26
 3.3        - Standard Types ................................   26
 3.4        - Encoding ASCII in Printable String ............   28
 4          - Addressing ....................................   30
 4.1        - A textual representation of MTS.ORAddress .....   30
 4.2        - Basic Representation ..........................   31
 4.3        - EBNF.822-address <-> MTS.ORAddress ............   36
 4.4        - Repeated Mappings .............................   48
 4.5        - Directory Names ...............................   50
 4.6        - MTS Mappings ..................................   50
 4.7        - IPMS Mappings .................................   55
 5          - Detailed Mappings .............................   59
 5.1        - RFC 822 -> X.400 ..............................   59
 5.2        - Return of Contents ............................   67
 5.3        - X.400 -> RFC 822 ..............................   67
 Appendix A - Mappings Specific to SMTP .....................   91
 Appendix B - Mappings specific to the JNT Mail .............   91
 1          - Introduction ..................................   91
 2          - Domain Ordering ...............................   91
 3          - Addressing ....................................   91
 4          - Acknowledge-To:  ..............................   91
 5          - Trace .........................................   92
 6          - Timezone specification ........................   92
 7          - Lack of 822-MTS originator specification ......   92
 Appendix C - Mappings specific to UUCP Mail ................   93
 Appendix D - Object Identifier Assignment ..................   94
 Appendix E - BNF Summary ...................................   94
 Appendix F - Format of address mapping tables ..............  101
 1          - Global Mapping Information ....................  101
 2          - Syntax Definitions ............................  102
 3          - Table Lookups .................................  103
 4          - Domain -> O/R Address format ..................  104
 5          - O/R Address -> Domain format ..................  104
 6          - Domain -> O/R Address of Gateway table ........  104
 Appendix G - Mapping with X.400(1984) ......................  105
 Appendix H - RFC 822 Extensions for X.400 access ...........  106
 Appendix I - Conformance ...................................  106
 Appendix J - Change History: RFC 987, 1026, 1138, 1148 .....  107
 1          - Introduction ..................................  108
 2          - Service Elements ..............................  108
 3          - Basic Mappings ................................  108

Hardcastle-Kille [Page 2] RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992

 4          - Addressing ....................................  108
 5          - Detailed Mappings .............................  109
 6          - Appendices ....................................  109
 Appendix K - Change History: RFC 1148 to this Document .....  109
 1          - General .......................................  109
 2          - Basic Mappings ................................  110
 3          - Addressing ....................................  110
 4          - Detailed Mappings .............................  110
 5          - Appendices ....................................  110
 References .................................................  111
 Security Considerations ....................................  113
 Author's Address ...........................................  113

Chapter 1 – Overview

1.1. X.400

 This document relates to the CCITT 1988 X.400 Series Recommendations
 / ISO IEC 10021 on the Message Oriented Text Interchange Service
 (MOTIS).  This ISO/CCITT standard is referred to in this document as
 "X.400", which is a convenient shorthand.  Any reference to the 1984
 CCITT Recommendations will be explicit.  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.  It is expected that X.400
 will be implemented very widely.

1.2. RFC 822

 RFC 822 evolved as a messaging standard on the DARPA (the US Defense
 Advanced Research Projects Agency) Internet.  It specifies and end to
 end message format.  It is used in conjunction with a number of
 different message transfer protocol environments.
 SMTP Networks
     On the DARPA Internet and other TCP/IP networks, RFC 822 is
     used in conjunction with two other standards: RFC 821, also
     known as Simple Mail Transfer Protocol (SMTP) [Postel82a],
     and RFC 920 which is a Specification for domains and a
     distributed name service [Postel84a].
 UUCP Networks
     UUCP is the UNIX to UNIX CoPy protocol, which is usually
     used over dialup telephone networks to provide a simple
     message transfer mechanism.  There are some extensions to
     RFC 822, particularly in the addressing.  They use domains
     which conform to RFC 920, but not the corresponding domain
     nameservers [Horton86a].

Hardcastle-Kille [Page 3] RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992

 Bitnet
     Some parts of Bitnet and related networks use RFC 822
     related protocols, with EBCDIC encoding.
 JNT Mail Networks
     A number of X.25 networks, particularly those associated
     with the UK Academic Community, use the JNT (Joint Network
     Team) Mail Protocol, also known as Greybook [Kille84a].
     This is used with domains and name service specified by the
     JNT NRS (Name Registration Scheme) [Larmouth83a].
 The mappings specified here are appropriate for all of these
 networks.

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.

Hardcastle-Kille [Page 4] RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992

 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
      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,
 [CCITT/ISO88b] 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 IP 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.

Hardcastle-Kille [Page 5] RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992

 The Reception service also allows for receipt of Delivery Reports
 DR), which indicate delivery success or failure.
 These IPMS Services utilise the Message Transfer (MT) Abstract
 Service [CCITT/ISO88c].  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 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 as these are neither mandatory in SMTP, nor available in other
 822-MTS protocols, they are not considered here.  Details of aspects
 specific to two 822-MTS protocols are given in Appendices B and C.
 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.  Most of these fields are analogous to P2
 heading fields, although some are analogous to MTS Service Elements

Hardcastle-Kille [Page 6] RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992

 or MTA Service Elements.

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 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 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 822-MTS
 information is always mapped into an IPM (MTA, MTS, and IPMS
 Services).  Going from X.400 to RFC 822, an RFC 822 message and the
 associated 822-MTS information may be derived from:
 1.   A Report (MTA, and MTS Services)
 2.   An IPN (MTA, MTS, and IPMS services)
 3.   An IPM (MTA, MTS, and IPMS services)
 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.

1.5.4. Repeated Mappings

 The primary goal of this specification is to support single 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.

Hardcastle-Kille [Page 7] RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992

 Where an X.400 messages 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 G 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 G.

1.7. Compatibility with previous versions

 The changes between this and older versions of the document are given
 in Appendices I and J.    These are RFCs 987, 1026, 1138, and 1148.
 This document is a revision of RFC 1148 [Kille90a].  As far as
 possible, changes have been made in a compatible fashion.

1.8. Aspects not covered

 There have been a number of cases where RFC 987 was 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:
  1. Extensions of RFC 822 to provide access to all X.400

services

  1. X.400 user interface definition
  1. Mapping X.400 to extended versions of RFC 822, with support

for multimedia content.

 The first two of 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

Hardcastle-Kille [Page 8] RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992

 all X.400 services.  Thus, it will be a poor choice for X.400
 implementors to use RFC 987(88) 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 H.

1.9. 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 strongly
 discouraged.

1.10. 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 eleven appendices.
 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.

1.11. 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.

Hardcastle-Kille [Page 9] RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992

 A number of comments from people on RFC 1148 lead to this document.
 In particular, there were comments and suggestions from:  Maurice
 Abraham (HP); Harald Alvestrand (Sintef); Peter Cowen (X-Tel); Jim
 Craigie (JNT); Ella Gardener (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).

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

Hardcastle-Kille [Page 10] RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992

 partial support, the level of partial support is 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:
  1. Semantic correspondence.
  1. No (significant) loss of information.
  1. 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.

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).

Hardcastle-Kille [Page 11] RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992

 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.
 Keywords:
      Supported by use of a heading extension.
 Subject:
      Supported.
 Comments:
      Supported by use of an extra body part.

Hardcastle-Kille [Page 12] RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992

 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.

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

Hardcastle-Kille [Page 13] RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992

 Autoforwarded:
 Content-Identifier:
 Conversion:
 Conversion-With-Loss:
 Delivery-Date:
 Discarded-X400-IPMS-Extensions:
 Discarded-X400-MTS-Extensions:
 DL-Expansion-History:
 Deferred-Delivery:
 Expiry-Date:
 Importance:
 Incomplete-Copy:
 Language:
 Latest-Delivery-Time:
 Message-Type:
 Obsoletes:
 Original-Encoded-Information-Types:
 Originator-Return-Address:
 Priority:
 Reply-By:
 Requested-Delivery-Method:
 Sensitivity:
 X400-Content-Type:
 X400-MTS-Identifier:

Hardcastle-Kille [Page 14] RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992

 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.  It is intended that
 these fields will be registered, and that co- operating RFC 822
 systems may 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)
      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-

Hardcastle-Kille [Page 15] RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992

 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:).
 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
      previous service).
 Non-delivery Notification
      Not supported, although in general an RFC 822 system 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
      Some types supported.  IA5 is fully supported.
      ForwardedIPMessage is supported, with some loss of
      information.  Other types get some measure of support,
      dependent on X.400 facilities for conversion to IA5.  This

Hardcastle-Kille [Page 16] RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992

      will only be done where content conversion is not
      prohibited.
 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
      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.

Hardcastle-Kille [Page 17] RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992

 Content Integrity
      Not supported.
 Conversion Prohibition
      Supported.  In this case, only messages with IA5 body parts,
      other body parts which contain only IA5, and Forwarded IP
      Messages (subject recursively to the same restrictions),
      will be mapped.
 Conversion Prohibition in Case of Loss of Information
      Supported.
 Counter Collection
      N/A (PDAU).
 Counter Collection with Advice
      N/A (PDAU).
 Cross Referencing Indication
      Supported.
 Deferred Delivery
      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.  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.

Hardcastle-Kille [Page 18] RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992

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 as
    an informal redistribution mechanism, beyond the scope of
    this control.  Messages will be sent to RFC 822,
    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

    Supported as new RFC 822 header (Expiry-Date:).  In general,
    no automatic action can be expected.

Explicit Conversion

    N/A (prior).

Forwarded IP Message Indication

    Supported, with some loss of information.  The message is
    forwarded 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 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.

Hardcastle-Kille [Page 19] RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992

Message Origin Authentication

    N/A (reception).

Message Security Labelling

    Not supported.

Message Sequence Integrity

    Not supported.

Multi-Destination Delivery

    Supported.

Multi-part Body

    Supported, with some loss of information, in that the
    structuring cannot be formalised in RFC 822.

Non Receipt Notification Request

    Not supported.

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).

Hardcastle-Kille [Page 20] RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992

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, as delivery notifications cannot be generated by
    RFC 822.  In practice, errors will be returned as IP
    Messages, and so this service may appear not to be supported
    see Non-delivery Notification).

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 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,
    this service is supported, although in practice it may
    appear that it is not supported.

Registered Mail

    N/A (PDAU).

Hardcastle-Kille [Page 21] RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992

Registered Mail to Addressee in Person

    N/A (PDAU).

Reply Request Indication

    Supported as comment next to address.

Replying IP Message Indication

    Supported.

Report Origin Authentication

    N/A (reception).

Request for Forwarding Address

    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

    In principle, 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.

Hardcastle-Kille [Page 22] RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992

Undeliverable Mail with Return of Physical Message

    N/A (PDAU).

Use of Distribution List

    In principle this applies only to X.400 supported
    distribution lists (see DL Expansion Prohibited).
    Theoretically, this service is N/A (prior).  In practice,
    because of informal RFC 822 lists, this service can be
    regarded as 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
 Primary and Copy Recipients Indication

Hardcastle-Kille [Page 23] RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992

 Replying IP Message Indication
 Subject Indication

2.3.2.3. New Services

 A new 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, which
 are received by an X.400 UA.

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 [Crocker82a].  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
      components).  In this case, the lexical analysis defined in
      Section 3 of RFC 822 shall be used.  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.  In these cases, 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.

Hardcastle-Kille [Page 24] RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992

  1. Around the ":" in all headers
  1. EBNF.labelled-integer
  1. EBNF.object-identifier
  1. EBNF.encoded-info
 RFC 822 folding rules are applied to all headers.

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.
 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.
 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] .

Hardcastle-Kille [Page 25] RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992

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, and some of the types
 defined in ASN.1 [CCITT/ISO88d].  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
 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, the mappings to IA5 defined
 in CCITT Recommendation X.408 (1988) shall be used [CCITT/ISO88a].
 These will then be encoded in ASCII.

Hardcastle-Kille [Page 26] RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992

 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 are mapped simply.  Other octets 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 ]
 The natural mapping is restricted to EBNF.ps-char, in order to 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

Hardcastle-Kille [Page 27] RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992

 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 "-">

3.3.7. Object Identifier

 Object identifiers are represented in a form similar to that 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)
      or
      (2) (6) (1)(11)(0)

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.

Hardcastle-Kille [Page 28] RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992

      ps-encoded       = *( ps-restricted-char / ps-encoded-char )
      ps-encoded-char  = "(a)"               ; (@)
                       / "(p)"               ; (%)
                       / "(b)"               ; (!)
                       / "(q)"               ; (")
                       / "(u)"               ; (_)
                       / "(l)"               ; "("
                       / "(r)"               ; ")"
                       / "(" 3DIGIT ")"
 The 822.3DIGIT in EBNF.ps-encoded-char must have range 0-127, and 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.

Hardcastle-Kille [Page 29] RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992

 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)             <->   ~
              (                 ->    (
              (l)               <->   (

Chapter 4 - Addressing

 Addressing is probably the trickiest problem of an X.400 <-> RFC 822
 gateway.  Therefore it is given a separate chapter.  This chapter, as
 a side effect, also defines a textual representation of an X.400 O/R
 Address.
 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 822-MTS 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.

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.

Hardcastle-Kille [Page 30] RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992

4.2. Basic 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 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

Hardcastle-Kille [Page 31] RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992

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 18.3.25 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

 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
                 I     labelled-integer
                 X     presentation-address
 The BNF for presentation-address is taken from the specification "A
 String Encoding of Presentation Address" [Kille89a].
 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 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,

Hardcastle-Kille [Page 32] RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992

 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.
 Recently, ISO has undertaken work to specify a string form of O/R
 Address [CCITT/ISO91a].  This has specified a number of string
 keywords for attributes.  As RFC 1148 was an input to this work, many
 of the keywords are the same.  To increase compatability, 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
             X121               X.121
             UA-ID              N-ID
             PD-OFFICE-NUMBER   PD-OFFICE NUMBER
 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.

4.2.1. 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
 2.   Initials contain only letters
 3.   Given Name 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.

Hardcastle-Kille [Page 33] RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992

 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 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 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!

4.2.2. Standard Encoding of MTS.ORAddress

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

Hardcastle-Kille [Page 34] RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992

      std-or-address  = 1*( "/" attribute "=" value ) "/"
      attribute       = standard-type
                      / "RFC-822"
                      / registered-dd-type
                      / dd-key "." std-printablestring
      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        = "$" ps-char
 The standard-type is any key defined in the table in Section 4.2,
 except PN, and DD.  The BNF leads to a set of attribute/value pairs.
 The value is interpreted according to the EBNF encoding defined in
 the table.
 If the standard-type is PN, the value is interpreted according to
 EBNF.encoded-pn, and the components of MTS.PersonalName and/or
 MTS.TeletexPersonalName derived accordingly.
 If dd-key is the recognised Domain Defined string (DD), then the type
 and value are interpreted according to the syntax implied from the
 encoding, and aligned to either the teletex or printable string form.
 Key and value shall have the same encoding.
 If value is "RFC-822", then the (printable string) Domain Defined
 Type of "RFC-822" is assumed.  This is an optimised encoding of the
 domain defined type defined by this specification.
 The matching of all keywords shall be done in a case-independent
 manner.
 EBNF.std-or-address uses the characters "/" and "=" as delimiters.
 Domain Defined Attributes and any value may contain these characters.
 A quoting mechanism, using the non-printable string "$" 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

Hardcastle-Kille [Page 35] RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992

 accordingly.  This restriction maximises the syntax checking which
 can be done at a gateway.

4.3. EBNF.822-address ↔ MTS.ORAddress

 Ideally, the mapping specified 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
      awkward.
 2.   In the general case, there would not be the necessary
      administrative co-operation between the X.400 and RFC 822
      worlds, which would be needed for this to work.
 Therefore, an asymmetrical mapping is defined, which can be
 symmetrical where there is appropriate administrative control.

4.3.1. X.400 encoded in RFC 822

 The std-or-address syntax is  used to encode O/R Address information
 in the 822.local-part of EBNF.822-address.  In some cases, further
 O/R Address information is associated with the 822.domain component.
 This cannot be used in the general case, due to character set
 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 imposed by
 domain conventions and policy, and by restrictions in RFC 821.
 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.  The following O/R Address attributes are considered

Hardcastle-Kille [Page 36] RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992

 as a hierarchy, and may be specified by the domain.  They are (in
 order of hierarchy):
      Country, ADMD, PRMD, Organisation, Organisational Unit
 There may be multiple Organisational Units.
 A global mapping is defined between domain specifications, and some
 set of attributes.  This association proceeds hierarchically.  For
 example, if a domain implies ADMD, it also implies country.
 Subdomains under this are associated according to the O/R Address
 hierarchy.  For example:
      => "AC.UK" might be associated with
      C="GB", ADMD="GOLD 400", PRMD="UK.AC"
      then domain "R-D.Salford.AC.UK" maps with
      C="GB", ADMD="GOLD 400", PRMD="UK.AC", O="Salford", OU="R-D"
 There are three basic reasons why a domain/attribute mapping might be
 maintained, as opposed to using simply subdomains:
 1.   As a shorthand to avoid redundant X.400 information.  In
      particular, there will often be only one ADMD per country,
      and so it does not need to be given explicitly.
 2.   To deal with cases where attribute values do not fit the
      syntax:
         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.
 3.   To deal with missing elements in the hierarchy.  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 omitted
      value shall be skipped.  For example, if "HNE.EGM" is
      associated with "C=TC", "ADMD=ECQ", "PRMD=HNE", and omitted
      organisation, then "ZI.HNE.EGM" is mapped with "C=TC",
      "ADMD=ECQ", "PRMD=HNE", "OU=ZI". Attributes may have null
      values, and  this is treated separately from omitted
      attributes (whilst it would be bad practice to treat these

Hardcastle-Kille [Page 37] RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992

      two cases differently, they must be allowed for).
 This set of mappings needs  be known by the gateways relaying between
 the RFC 822 world, and the O/R Address space associated with the
 mapping in question.  There needs to be a single global definition of
 this set of mappings.  A mapping implies an adminstrative equivalence
 between the two parts of the namespaces which are mapped together.
 To correctly route in all cases, it is necessary for all gateways to
 know the mapping.  To facilitate distribution of a global set of
 mappings, a format for the exchange of this information is defined in
 Appendix F.
 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:
      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"
 The first three attributes are determined by the domain Widget.COM.
 Then, the first element of OrganizationalUnitNames is determined
 systematically, and the remaining attributes are encoded on the LHS.
 In an extreme case, all of the attributes will be on the LHS.  As the
 domain cannot be null, the RHS will simply be a domain indicating the
 gateway.
 The RHS (domain) encoding is designed to deal cleanly with common
 addresses, and so the amount of information on the RHS is maximised.
 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.  Use of other forms of O/R Address, and teletex encoded
 attributes will require an LHS encoding.
 There is a further mechanism to simplify the encoding of common
 cases, where the only attributes to be encoded on the LHS is a (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 previous example O/R Address, it would map
 with the RFC 822 address: J.Linnimouth@Marketing.Widget.COM.

Hardcastle-Kille [Page 38] RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992

 From the standpoint of the RFC 822 Message Transfer System, the
 domain specification is simply 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.  In
 most cases, this will be done by registering the higher levels, and
 assuming that the gateway can handle the lower levels.

4.3.2. RFC 822 encoded in X.400

 In some cases, the encoding defined above may be reversed, to give a
 "natural" encoding of genuine RFC 822 addresses.  This depends
 largely on the allocation of appropriate management domains.
 The general case is mapped by use of domain defined 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 depends on the
 context of the gateway.
 1.   In the context of RFC 822, and RFC 920
      [Crocker82a,Postel84a], the string can be used directly.
 2.   In the context of the JNT Mail protocol, and the NRS
      [Kille84a,Larmouth83a], the string shall be interpreted
      according to Mailgroup Note 15 [Kille84b].
 3.   In the context of UUCP based systems, the string shall be
      interpreted as defined in [Horton86a].
 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:
         C               = "GB"
         ADMD            = "GOLD 400"
         PRMD            = "UK.AC"
         O               = "UCL"
         OU              = "CS"
         "RFC-822"      =  "Jimmy(a)WIDGET-LABS.CO.UK"
 OR
         C               = "TC"
         ADMD            = "Wizz.mail"
         PRMD            = "42"
         "rfc-822"       = "postel(a)venera.isi.edu"

Hardcastle-Kille [Page 39] RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992

 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 exceeeds 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, analagous with 4.3.1, a means to associate parts of the O/R
 Address hierarchy with domains.  There is an analogous 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, Organisational Units (printable
 string and teletex forms) and Domain Defined 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
      (Organisational 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 Organisation
      Attribute, it shall be to the right of any Organisational
      Unit attributes.  These requirements are for the following
      reasons:

Hardcastle-Kille [Page 40] RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992

  1. Alignment to the hierarchy of other components in RFC

822 addresses (thus, Organisational 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.
  1. Backwards compatibility with RFC 987/1026.
  1. 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
      822.msg-id, this order shall be followed.
 2.   For the Organisational 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
      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

 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

Hardcastle-Kille [Page 41] RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992

      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.  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.  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:
  • ( domain-syntax "." ) known-domain
      Where EBNF.known-domain is the longest possible match in the
      set of globally defined mappings (see Appendix F).  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,
      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 space go to
      stage II.
 4.   If the unquoted 822.local-part contains any characters not
      in PrintableString, go to stage II.
 5.   Parse the (unquoted) 822.local-part according to the EBNF
      EBNF.std-or-address.  Checking of upper bounds should not be

Hardcastle-Kille [Page 42] RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992

      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
      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 dericed attributes which
      are more significant thant the most signicant 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).  therwise 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
      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 discussed in Section

Hardcastle-Kille [Page 43] RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992

 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 throug 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 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.  The table format for distribution of this information
      is defined in Appendix F.
      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
      (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
      it prefers to use.
 822-MTS Recipient
      As the RFC 822 and X.400 worlds are fully connected, there

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      is no technical reason for this situation to occur.  In some
      cases, routing may be configured to connect two parts of the
      RFC 822 world using X.400.  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.

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:
 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 may facilitate users used to this
      delimiter.
      colon-or-address = 1*(attribute "=" value ";" *(LWSP-char))
 The remaining heuristic relates to ordering of address components.
 The ordering of attributes may be inverted or mixed.  For this
 reason, the following heuristics may be applied:
 4.   If there is an Organisation attribute to the left of any Org
      Unit attribute, assume that the hierarchy is inverted.

4.3.5. X.400 → RFC 822

 There are two basic cases:
 1.   RFC 822 addresses encoded in X.400.

Hardcastle-Kille [Page 45] RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992

 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.  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 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.

Mapping A

 1.   Map the domain defined attribute value to ASCII, as defined
      in Chapter 3.

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
      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
      orginal values should be used.
 2.   Map numeric country codes to the two letter values.

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 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,
      and go to step 5.
 Note:     It might be appropriate to use a non-local domain.
           This would be selected by a global mapping analagous to
           the one described at the end of 4.3.4.  This is not
           done, primarily because use of RFC 822 to connect X.400
           systems is not expected to be significant.
      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.
 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
      attributes remaining in the O/R address shall be encoded on
      the LHS.  This is to ensure a reversible mapping. For
      example, if the is an addres /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 is not  mnemonic form (form 1 variant 1),
      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

Hardcastle-Kille [Page 47] RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992

      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 [Kille89b] may be appropriate.  Use of this mapping is
      discouraged.

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 recurive at a single
 gateway.  For example:
         C          = "XX"
         ADMD       = "YY"
         O          = "ZZ"
         "RFC-822"  = "Smith(a)ZZ.YY.XX"
 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 belongs to.  The

Hardcastle-Kille [Page 48] RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992

 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"
         Organisation    = "Widget Corporation"
         Surname         = "Soap"
         Given Name      = "Joe"
 This is then routed to another gateway where the mapping is reversed
 to give:
         Joe.Soap@Widget.PTT.XY
 Here, use of the gateway is transparent.
 Mappings will only be symmetrical where mapping tables 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:
       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

Hardcastle-Kille [Page 49] RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992

 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

"/C=UK/ADMD=BT/PRMD=AC/RFC-822=jj(a)seismo.css.gov/"@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
 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.
 Note:There is ongoing work on specification of a "user friendly"
      format for directory names.  If this is adopted as an
      internet standard, it will be recommended, but not required,
      for use here.

4.6. MTS Mappings

 The basic mappings at the MTS level are:
 1) 822-MTS originator ->
               MTS.PerMessageSubmissionFields.originator-name
    MTS.OtherMessageDeliveryFields.originator-name ->
               822-MTS originator
 2) 822-MTS recipient ->
               MTS.PerRecipientMessageSubmissionFields
    MTS.OtherMessageDeliveryFields.this-recipient-name ->
               822-MTS recipient
 822-MTS recipients and return addresses are encoded as EBNF.822-

Hardcastle-Kille [Page 50] RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992

 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

 From the 822-MTS 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.
 recipient-name
      This is derived from the 822-MTS 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

4.6.2. X.400 → RFC 822

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

4.6.2.1. 822-MTS Mappings

 Use the basic ORAddress mapping, to generate the 822-MTS 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).

Hardcastle-Kille [Page 51] RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992

 The 822-MTS 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 recipient according to the basic ORAddress
 mapping, discarding MTS.ORName.directory-name if present.  However,
 if this model was followed exactly, there would be no possibility to
 have multiple 822-MTS 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 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
 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
 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 the per-recipient information, and insert a field:
              X400-Recipients: non-disclosure:;

Hardcastle-Kille [Page 52] RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992

      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 descrined in 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:
         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"
 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.

Hardcastle-Kille [Page 53] RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992

 requested-delivery-method
 physical-forwarding-prohibited
      "(Physical Forwarding Prohibited)".
 physical-forwarding-address-request
      "(Physical Forwarding Address Requested)".
 physical-delivery-modes
 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 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, 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.

Hardcastle-Kille [Page 54] RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992

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.  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):
  1. The 822.phrase component if the 822.address is an

822.phrase 822.route-addr construct.

  1. Any 822.comments, in order, retaining the parentheses.
      This string is then encoded into T.61 use a human oriented
      mapping (as described in Chapter 3).  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 (none and false).
 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, and a IPMS.ORDescriptor with only an
 free-form-name component built from it.

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

Hardcastle-Kille [Page 55] RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992

      EBNF.822-address.
 2a.  If IPMS.ORDescriptor.free-form-name is present, convert it
      to ASCII (Chapter 3), 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 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 +44-1-387-7050)
 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)" is appended to the address.
      If both receipt and non-receipt notfications are requested,
      the comment relating to the latter may be omitted, to make
      the RFC 822 address cleaner.  The effort of correlating P1
      and P2 information is too great to justify the gateway
      sending Receipt Notifications.
 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,

Hardcastle-Kille [Page 56] RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992

 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 allows for good things to
 happen 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:
  1. There is no major requirement to make message IDs "natural"
  1. 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).
 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.

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 built as
         [ printablestring ] "*"  [ std-or-address ]
 with EBNF.printablestring being the IPMS.IPMIdentifier.user-
 relative-identifier, and std-or-address being an encoding of the
 IPMS.IPMIdentifier.user.  If necessary, the 822.quoted-string
 encoding is used.  For example:
 <"147*/S=Dietrich/O=Siemens/ADMD=DBP/C=DE/"@MHS>

Hardcastle-Kille [Page 57] RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992

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.
 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.

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:" 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

Hardcastle-Kille [Page 58] RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992

 implementation of this standard is encouraged to recognise message
 IDs generated by RFC 987.  This is not required.
 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 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.

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

5.1.1. Basic Approach

 A single IP Message is generated from an RFC 822 message The RFC 822
 headers are used to generate the IPMS.Heading.  The IP Message will
 have one IA5 IPMS.BodyPart containing the RFC 822 message body.
 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:
      rfc-822-field HEADING-EXTENSION
              VALUE RFC822FieldList
              ::= id-rfc-822-field-list

Hardcastle-Kille [Page 59] RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992

      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"). Structured 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 usually consists of one IPMS.BodyPart
 of type IPMS.IA5TextBodyPart with
 IPMS.IA5TextBodyPart.parameters.repertoire set to the default (ia5)
 which contains the body of the RFC 822 message.  The exception is
 where there is a "Comments:" field in the RFC 822 header.
 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 must be
 considered.  At the MTS and MTA level, this specification is strict
 about enforcing upper bounds. Three options are available at the IPM
 level.  Use of any of these options conforms to this standard.
 1.   Ignore upper bounds, and generate messages in the natural
      manner.  This assumes that if any truncation is done, it
      will happen at the recipient UA.  This will maximise
      transfer of information, but is likely break some recipient
      UAs.
 2.   Reject any inbound message which would cause a message
      violating constraints to be generated.  This will be robust,
      but may prevent useful communication.
 3.   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.

Hardcastle-Kille [Page 60] RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992

      If the Free Form name is truncated, it may lead to breaking
      RFC 822 comments, which will cause an awkward reverse
      mapping.
 These options have different advantages and disadvantages, and the
 choice will depend on the exact application of the gateway.
 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.

Hardcastle-Kille [Page 61] RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992

 In-Reply-To:
      If there is one value, it is mapped to
      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 Chapter 3 from ASCII to
      T.61.
 Comments:
      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: ".  This body part shall precede
      the other one.
 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.
 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).

5.1.4. Mappings to the MTS Abstract Service

 The MTS.MessageSubmissionEnvelope comprises
 MTS.PerMessageSubmissionFields, and

Hardcastle-Kille [Page 62] RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992

 MTS.PerRecipientMessageSubmissionFields.  The mandatory parameters
 are defaulted as follows.
 MTS.PerMessageSubmissionFields.originator-name
      This is always generated from 822-MTS, 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, 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:
  1. Alternate recipient is allowed, as it seems desirable to

maximise the opportunity for (reliable) delivery.

  1. Content return request is set according to the issues

discussed in Section 5.2.

 MTS.PerMessageSubmissionFields.original-encoded-information-types is
 a set of one element BuiltInEncodedInformationTypes.ia5-text.
 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.  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).

5.1.5. Mappings to the MTA Abstract Service

 There is a need to map directly onto some aspects of the MTA Abstract

Hardcastle-Kille [Page 63] RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992

 service, for the following reasons:
  1. So the the MTS Message Identifier can be generated from the

RFC 822 Message-ID:.

  1. So that the submission date can be generated from the

822.Date.

  1. To prevent loss of trace information
  1. 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.
 Date:
      This is used to set the first component of
      MTA.PerMessageTransferFields.trace-information
      (MTA.TraceInformationElement).  The 822-MTS 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
      MTA.PerMessageTransferFields.internal-trace-information is
      generated in an analogous manner, although this can be
      dropped later in certain circumstances (see the procedures
      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.

Hardcastle-Kille [Page 64] RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992

      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 are processed (X400-Received: in all cases and Via:
      if Appendix B is supported), the relative ordering 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.
      Then add a new element (MTA.InternalTraceInformationElement)
      to MTA.PerMessageTransferFields.internal-trace-information,
      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
        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

Hardcastle-Kille [Page 65] RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992

 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.

5.1.6. 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 gateway conforming to this
 specification does not need to map all of these fields to X.400.
 Two  extended fields must be mapped, 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 element of trace can be taken from the first X400-Received:.
 Some field that shall not be mapped, and should be discarded.  The
 following cannot be mapped back:
  1. Discarded-X400-MTS-Extensions:
  1. Message-Type:
  1. Discarded-X400-IPMS-Extensions:
 If Message-Type: is set to "Multiple Part", then the messge is
 encoded according to RFC 934, and this may be mapped on to the
 corresponding X.400 structures.
 The following may cause problems, due to other information not being
 mapped back (e.g., extension numbers), or due to changes made on the
 RFC 822 side due to list expansion:
  1. X400-Content-Type:
  1. X400-Originator:

Hardcastle-Kille [Page 66] RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992

  1. X400-Recipients:
  1. 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 this reverse mapping should be indicated in the gateway
 conformace statement.

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.
 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

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

Hardcastle-Kille [Page 67] RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992

 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 recipients.

5.3.2. RFC 822 Settings

 An RFC 822 Service requires to have a number of mandatory fields in
 the RFC 822 Header.  Some 822-MTS services mandate specification of
 an 822-MTS Originator.  Even in cases where this is optional, it is
 usually desirable to specify a value.  The following defaults are
 defined, which shall be used if the mappings specified do not derive
 a value:
 822-MTS 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 Originator.  If this is gateway
      generated, an appropriate 822.phrase shall be added.
 At least one recipient field
      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:
         encoded-info    = 1#encoded-type
         encoded-type    = built-in-eit / object-identifier
         built-in-eit    = "Undefined"         ; undefined (0)

Hardcastle-Kille [Page 68] RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992

                         / "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 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:
      ipms-field = "Obsoletes" ":" 1#msg-id
                 / "Expiry-Date" ":" date-time
                 / "Reply-By" ":" date-time
                 / "Importance" ":" importance
                 / "Sensitivity" ":" sensitivity
                 / "Autoforwarded" ":" boolean
                 / "Incomplete-Copy" ":"
                 / "Language" ":" language
                 / "Message-Type" ":" message-type
                 / "Discarded-X400-IPMS-Extensions" ":" 1#oid
      importance      = "low" / "normal" / "high"
      sensitivity     = "Personal" / "Private" /

Hardcastle-Kille [Page 69] RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992

                             "Company-Confidential"
      language        = 2*ALPHA [ language-description ]
      language-description = printable-string
      message-type    = "Delivery Report"
                      / "InterPersonal Notification"
                      / "Multiple Part"
 The mappings and actions for the IPMS.Heading is now specified for
 each element.  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, execpt for
 IPMS.Heading.blind-copy-recipients, which can be mapped onto BCC:
 (the only RFC 822 field which allows zero recipients).
 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:".

Hardcastle-Kille [Page 70] RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992

 IPMS.Heading.subject
      Mapped to "Subject:".  The contents are converted to ASCII
      (as defined in Chapter 3).  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:".
 IPMS.Heading.reply-time
      Mapped to the extended RFC 822 field "Reply-By:".
 IPMS.Heading.reply-recipients
      Mapped to "Reply-To:".
 IPMS.Heading.importance
      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 extended RFC 822 field "Language:", filling in
      the two letter code. The language-description may filled in
      with a human readable description of the language, and it is
      recommended to do this.
 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:".
 The IPMS.Body is mapped into the RFC 822 message body.  Each
 IPMS.BodyPart is converted to ASCII as follows:

Hardcastle-Kille [Page 71] RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992

 IPMS.IA5Text
      The mapping is straightforward (see Chapter 3).
 IPMS.MessageBodyPart
      The 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:".
 Other
      If other body parts can be mapped to IA5, either by use of
      mappings defined in X.408 [CCITT88a], or by other reasonable
      mappings, this shall be done unless content conversion is
      prohibited.
 If some or all of the body parts cannot be converted there are three
 options.  All of these conform to this standard.  A different choice
 may be made for the case where no body part can be converted:
 1.   The first option is to reject the message, and send a non-
      delivery notification.  This must always be done if
      conversion is prohibited.
 2.   The second option is to map a missing body part to something
      of the style:
              There was a foobarhere
              The widget gateway ate it
      This will allow some useful information to be transferred.
      As the recipient is likely to be a human (IPMS), then
      suitable action will usually be possible.
 3.   Finally both may be done.  In this case, the supplementary
      information in the (positive) Delivery Report shall make
      clear that something was sent on to the recipient with
      substantial loss of information.
 Where there is more than one IPMS.BodyPart, the mapping defined by
 Rose and Stefferud in [Rose85a], is used to map the separate
 IPMS.BodyParts in the single RFC 822 message body.  If this is done,

Hardcastle-Kille [Page 72] RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992

 a "Message-Type:" field with value "Multiple part" shall be added,
 which will indicate to a receiving gateway that the message may be
 unfolded according to RFC 934.
 Note:There is currently work ongoing to produce an upgrade to RFC
      934, which also allows for support of body parts with non-
      ASCII content (MIME).  When this work is released as an RFC,
      this specification will be updated to refer to it instead
      for RFC 934.
 For backwards compatibility with RFC 987, the following procedures
 shall also be followed.  If there are two IA5 body parts, and the
 first 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.
 An example message, illustrating a number of aspects is given below.

Return-Path:<@mhs-relay.ac.uk:stephen.harrison@gosip-uk.hmg.gold-400.gb> 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 X400-Content-Type: P2-1984 (2) 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 (Receipt Notification Requested) (Non Receipt Notification Requested), Tony Bates tony@ean-relay.ac.uk (Receipt Notification Requested), Steve Kille S.Kille@cs.ucl.ac.uk (Receipt Notification Requested) Subject: Email Problems Sender: Stephen.Harrison@gosip-uk.hmg.gold-400.gb

—————————— Start of body part 1

Hope you gentlemen…….

Hardcastle-Kille [Page 73] RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992

Regards,

Stephen Harrison UK GOSIP Project

—————————— Start of forwarded message 1

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

- —————————— Start of body part 1

Dear Mr Harrison……

- —————————— End of body part 1

—————————— End of forwarded message 1

5.3.5. Mappings from an IP Notification

 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"
 References:
      Set to IPMS.IPN.subject-ipm
 The following EBNF is defined for the body of the Message.  This
 format is defined to ensure that all information from an

Hardcastle-Kille [Page 74] RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992

 interpersonal notification is available to the end user in a uniform
 manner.
      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:"
                        <CRLF> <CRLF> message
      preferred-recipient = mailbox
      receipt-time        = date-time
      auto-comment        = printablestring
      ipn-suppl           = printablestring
      discard-reason     = "Expired" / "Obsoleted" /
                              "User Subscription Terminated"

Hardcastle-Kille [Page 75] RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992

      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 an RFC 822 mapping of
      the message included.  Otherwise the first 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

Hardcastle-Kille [Page 76] RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992

 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.
         The following comment was made:
                 Sent on to a random destination
         The following information types were converted: g3fax

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:
      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#( oid / labelled-integer )
      prohibition     = "Prohibited" / "Allowed"
      mts-msg-id       = "[" global-id ";" *text "]"

Hardcastle-Kille [Page 77] RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992

      mts-content-type = "P2" /  labelled-integer
                      / object-identifer
      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:
 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 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.

Hardcastle-Kille [Page 78] RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992

 converted-encoded-information-types
      Discarded, as it will always be IA5 only.
 message-submission-time
      Mapped to Date:.
 content-identifier
      Mapped to the extended RFC 822 field "Content-Identifier:".
 If any extensions (MTS.MessageDeliveryEnvelope.other-
 fields.extensions) are 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

Hardcastle-Kille [Page 79] RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992

      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.
 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:
  1. Allowing for multiple recipients to share a single RFC 822

message

  1. Making the X.400 trace information available on the RFC 822

side

  1. Making any information on deferred delivery available
 The 822-MTS 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:
      mta-field       = "X400-Received" ":" x400-trace
                      / "Deferred-Delivery" ":" date-time

Hardcastle-Kille [Page 80] RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992

                      / "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 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) [Systems85a], 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 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.

Hardcastle-Kille [Page 81] RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992

 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.

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 is generated with the following fields:
 From:
      An administrator at the gateway system.  This is also the
      822-MTS originator.
 To:  A mapping of the
      MTA.ReportTransferEnvelope.report-destination-name.  This is
      also the 822-MTS recipient.
 Message-Type:
      Set to "Delivery Report".
 Subject:
      The EBNF for the subject line is:

Hardcastle-Kille [Page 82] RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992

       subject-line  = "Delivery-Report" "(" status ")"
                       [ "for" destination ]
       status        = "success" / "failure" / "success and failures"
       destination   = mailbox / "MTA" word
 The format of the body of the message 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 X.400,
 with the description in one body part, and a forwarded message
 (return of content) in the second.  This structure is useful to the
 RFC 822 recipient, as it enables the original message to be
 extracted.  The first body part is 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.

3. A clearly marked section which contains detailed information

   extracted from the report.  This is marked clearly, as it
   will not be comprehensible to the average user.  It is
   retained, as it may be critical to diagnosing an obscure
   problem.
   This section may be omitted in positive DRs, and it is
   recommended that this is appropriate for most gateways.
      dr-body-format = dr-summary <CRLF>
                      dr-recipients <CRLF>
                      dr-administrator-info-envelope <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

Hardcastle-Kille [Page 83] RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992

      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
      dr-administrator-info-envelope = 3*( "*" text <CRLF> )
      dr-administrator-info =
       "**** The following information is directed towards"
       "the local administrator" <CRLF>
       "**** and is not intended for the end user" <CRLF> <CRLF>
       "DR generated by:" report-point <CRLF>
       "at" date-time <CRLF> <CRLF>
       "Converted to RFC 822 at" mta <CRLF>
       "at" date-time <CRLF> <CRLF>
       "Delivery Report Contents:" <CRLF> <CRLF>
       drc-field-list <CRLF>
       "***** End of administration information"
      drc-field-list       = *(drc-field <CRLF>)
      drc-field = "Subject-Submision-Identifier" ":"
                                      mts-msg-id
                / "Content-Identifier" ":" printablestring
                / "Content-Type" ":" mts-content-type
                / "Original-Encoded-Information-Types" ":"
                              encoded-info
                / "Originator-and-DL-Expansion-History" ":"
                              dl-history
                / "Reporting-DL-Name" ":" mailbox
                / "Content-Correlator" ":" content-correlator
                / "Recipient-Info" ":" recipient-info
                / "Subject-Intermediate-Trace-Information" ":"
                                        x400-trace
      recipient-info  = mailbox "," std-or ";"
                  report-type
                  [ "converted eits" encoded-info ";" ]
                  [ "originally intended recipient"
                          mailbox "," std-or ";" ]
                  [ "last trace" [ encoded-info ] date-time ";" ]

Hardcastle-Kille [Page 84] RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992

                  [ "supplementary info" <"> printablestring <"> ";" ]
                  [ "redirection history" 1#redirection ";"
                  [ "physical forwarding address"
                                        printablestring ";" ]
      report-type     = "SUCCESS" drc-success
                      / "FAILURE" drc-failure
      drc-success     = "delivered at" date-time ";"
                      [ "type of MTS user" labelled-integer ";" ]
      drc-failure     = "reason" labelled-integer ";"
                      [ "diagnostic" labelled-integer ";" ]
      report-point = [ "mta" word "in" ] global-id
      content-correlator = *word
      dl-history = 1#( mailbox "(" date-time ")")
 The format is defined as a fixed definition of an the outer level
 (EBNF.dr-body-format).  The element EBNF.dr-administrator-info-
 envelope, provides a means of encapsulating a section of the header
 in a manner which is clear to the end user.  Each line of this
 section begins with "*".  Each element of EBNF.text within %EBNF.dr-
 administrator-info-envelope must not contain <CRLF>.  This is used to
 wrap up EBNF.dr-administrator-info, which will generate a sequenece
 of lines not starting with "*".  EBNF.drc-fields may be folded using
 the RFC 822 folding rules.
 The elements of MTS.ReportDeliveryEnvelope.per-report-fields are
 mapped as follows onto extended RFC 822 fields:
 subject-submission-identifier
      Mapped to EBNF.drc-field (Subject-Submission-Identifier)
 content-identifier
      Mapped to EBNF.drc-field (Content-Identifier).  This should
      also be used in EBNF.dr-summary if there is no Content
      Correlator present.
 content-type
      Mapped to EBNF.drc-field (Content-Type)
 original-encoded-information-types
      Mapped to EBNF.drc-field (Encoded-Info)

Hardcastle-Kille [Page 85] RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992

 The extensions from MTS.ReportDeliveryEnvelope.per-report-
 fields.extensions are mapped as follows:
 originator-and-DL-expansion-history
      Mapped to EBNF.drc-field (Originator-and-DL-Expansion-
      History)
 reporting-DL-name
      Mapped to EBNF.drc-field (Reporting-DL-Name)
 content-correlator
      Mapped to EBNF.content-correlator, provided that the
      encoding is IA5String (this will always be the case).  This
      is used in EBNF.dr-summary and EBNF.drc-field-list.  In the
      former, LWSP may be added, in order to improve the layout of
      the message.
 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.
 For each element of MTS.ReportDeliveryEnvelope.per-recipient-fields,
 a value of EBNF.dr-recipient, and an EBNF.drc-field (Recipient-Info)
 is generated.  The components are mapped as follows.
 actual-recipient-name
      Used to generate the first EBNF.mailbox and EBNF.std-or in
      EBNF.recipient-info.  Both RFC 822 and X.400 forms are
      given, as there may be a problem in the mapping tables.  It
      also generates the EBNF.mailbox in EBNF.dr-recip-success or
      EBNF.dr-recip-failure.
 report
      If it is MTS.Report.delivery, then set EBNF.dr-recipient to
      EBNF.dr-recip-success, and similarly set EBNF.report-type,
      filling in EBNF.drc-success.  If it is a failure, set
      EBNF.dr-recipient to EBNF.dr-recip-failure, making a human
      interpretation of the reason and diagnostic codes, and
      including any supplementary information.  EBNF.drc-failure
      is filled in systematically.
 converted-encoded-information-types
      Set EBNF.drc-field ("converted eits")

Hardcastle-Kille [Page 86] RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992

 originally-intended-recipient
      Set the second ("originally intended recipient") mailbox and
      std-or in EBNF.drc-field.
 supplementary-info
      Set EBNF.drc-field ("supplementary info"), and include this
      information in EBNF.dr-recip-failure.
 redirection-history
      Set EBNF.drc-field ("redirection history")
 physical-forwarding-address
      Set ENBF.drc-field ("physical forwarding address")
 recipient-certificate
      Discard
 proof-of-delivery
      Discard
 Any unknown extensions shall be discarded, irrespective of
 criticality.
 The original message, or an extract from it, shall be included in the
 delivery port if it is available.  The original message will usually
 be available at the gateway, as discussed in Section 5.2.  If the
 original message is available, but of erroneous format, a dump of the
 ASN.1 may be included.  This is recommended, but not required.

5.3.8.2. MTA Mappings

 The single 822-MTS recipient is constructed from
 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:
 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

Hardcastle-Kille [Page 87] RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992

 MTA.ReportTransferEnvelope.internal-trace-information
      Mapped onto the extended RFC 822 field "X400-Received:", as
      described in Section 5.3.7.  The first element is also used
      to generate the "Date:" field, and the EBNF.report-point.
 MTA.PerRecipientReportTransferFields.last-trace-information
      Mapped to EBNF.recipient-info (last trace)
 MTA.PerReportTransferFields.subject-intermediate-trace-
      information Mapped to EBNF.drc-field (Subject-Intermediate-
      Trace-Information). These fields are ordered so that the
      most recent trace element comes first.

5.3.8.3. Example Delivery Reports

 Example Delivery Report 1:
 Return-Path: <postmaster@cs.ucl.ac.uk>
 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>
 Content-Identifier: Greetings.
  1. —————————– Start of body part 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 following information is directed towards the local * administrator and is not intended for the end user * * DR generated by mta bells.cs.ucl.ac.uk * in /PRMD=uk.ac/ADMD=gold 400/C=gb/ * at Thu, 7 Feb 1991 15:48:34 +0000

Hardcastle-Kille [Page 88] RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992

* * Converted to RFC 822 at bells.cs.ucl.ac.uk * at Thu, 7 Feb 1991 15:48:40 +0000 * ….. continued on next page

* Delivery Report Contents: * * Subject-Submission-Identifier: * [/PRMD=uk.ac/ADMD=gold 400/C=gb/;1803.665941698@UK.AC.UCL.CS] * Content-Identifier: Greetings. * Subject-Intermediate-Trace-Information:

         /PRMD=uk.ac/ADMD=gold 400/C=gb/;

* arrival Thu, 7 Feb 1991 15:48:20 +0000 action Relayed

* Subject-Intermediate-Trace-Information:

         /PRMD=uk.ac/ADMD=gold 400/C=gb/;

* arrival Thu, 7 Feb 1991 15:48:18 +0000 action Relayed * Recipient-Info: H.Hildegard@bbn.com, * /RFC-822=H.Hildegard(a)bbn.com/OU=cs/O=ucl

        /PRMD=uk.ac/ADMD=gold 400/C=gb/;

* FAILURE reason Unable-To-Transfer (1); * diagnostic Unrecognised-ORName (0); * last trace (ia5) Thu, 7 Feb 1991 15:48:18 +0000; * supplementary info "MTA 'bbn.com' gives error message (USER) * Unknown user name in "H.Hildegard@bbn.com""; End of administration information The Original Message follows: —————————— Start of forwarded message 1 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 —————————— End of forwarded message 1 Example Delivery Report 2: Hardcastle-Kille [Page 89] RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992 Return-Path: postmaster@cs.ucl.ac.uk 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 15:49:11 +0000 Message-ID: <"DLE/910207154840Z/000"@cs.ucl.ac.uk> Content-Identifier: A useful mess… This report relates to your message: A useful mess… 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 following information is directed towards the local * administrator and is not intended for the end user * * DR generated by /PRMD=DGC/ADMD=GOLD 400/C=GB/ * at Thu, 7 Feb 1991 15:48:40 +0000 * * Converted to RFC 822 at bells.cs.ucl.ac.uk * at Thu, 7 Feb 1991 15:49:12 +0000 * * Delivery Report Contents: * * Subject-Submission-Identifier: * [/PRMD=uk.ac/ADMD=gold 400/C=gb/;1796.665941626@UK.AC.UCL.CS] * Content-Identifier: A useful mess… * Recipient-Info: j.nosuchuser@dle.cambridge.DGC.gold-400.gb, * /I=j/S=nosuchuser/OU=dle/O=cambridge/PRMD=DGC/ADMD=GOLD 400/C=GB/; * FAILURE reason Unable-To-Transfer (1); * diagnostic Unrecognised-ORName (0); * supplementary info "DG 21187: (CEO POA) Unknown addressee."; End of administration information

The Original Message is not available

Hardcastle-Kille [Page 90] RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992

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.

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 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.

Appendix B - Mappings specific to the JNT Mail

 This Appendix is specific to the JNT Mail Protocol.  It describes
 specific changes in the context of this protocol.
 1.  Introduction
    There are five aspects of a gateway which are JNT Mail Specific.
    These are each given a section of this appendix.
 2.  Domain Ordering
    When interpreting and generating domains, the UK NRS domain
    ordering shall be used, both in headers, and in text generated for
    human description.
 3.  Addressing
    A gateway which maps to JNT Mail should recognise the Domain
    Defined Attribute JNT-MAIL.  The value associated with this
    attribute should be interpreted according to the JNT Mail
    Specification.  This DDA shall never be generated by a gateway.
    For this reason, the overflow mechanism is not required.
 4.  Acknowledge-To:
    This field has no direct functional equivalent in X.400.  However,
    it can be supported to an extent, and can be used to improve X.400
    support.
    If an Acknowledge-To: field is present when going from JNT Mail to

Hardcastle-Kille [Page 91] RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992

    X.400, there are two different situations.  The first case is
    where there is one address in the Acknowledge-To: field, and it is
    equal to the 822-MTS return address.  In this case, the
    MTS.PerRecipientSubmissionFields.originator-request-report.report
    shall be set for each recipient, and the Acknowledge-To: field
    discarded.  Here, X.400 can provide the equivalent service.
    In all other cases two actions are taken.
       1. Acknowledgement(s) may be generated by the gateway.  The
          text of these acknowledgements shall indicate that they are
          generated by the gateway, and do not correspond to delivery.
       2. The Acknowledge-To: field shall be passed as an extension
          heading.
    When going from X.400 to JNT Mail, in cases where
    MTA.PerRecipientMessageTransferFields.per-recipient-indicators.
    originator-report bit is set for all recipients (i.e., there is a
    user request for a positive delivery report for every recipeint),
    generate an Acknowledge-To: field containing the
    MTS.OtherMessageDeliveryFields.originator-name.  Receipt
    notification requests are not mapped onto Acknowledge-To:, as no
    association can be guaranteed between IPMS and MTS level
    addressing information.
 5.  Trace
    JNT Mail trace uses the Via: syntax.  When going from JNT Mail to
    X.400, a mapping similar to that for Received:  is used. No
    MTS.GlobalDomainIdentifier of the site making the trace can be
    derived from the Via:, so a value for the gateway is used.  The
    trace text, including the "Via:", is unfolded, truncated to
    MTS.ub-mta-name-length (32), and mapped to
    MTA.InternalTraceInformationElement.mta-name.  There is no JNT
    Mail specific mapping for the reverse direction.
 6.  Timezone specification
    The extended syntax of zone defined in the JNT Mail Protocol shall
    be used in the mapping of UTCTime defined in Chapter 3.
 7.  Lack of 822-MTS originator specification
    In JNT Mail the default mapping of the
    MTS.OtherMessageDeliveryFields.originator-name is to the Sender:
    field.  This can cause a problem when going from X.400 to JNT Mail
    if the mapping of IPMS.Heading has already generated a Sender:

Hardcastle-Kille [Page 92] RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992

    field.  To overcome this, new extended JNT Mail field is defined.
    This is chosen to align with the JNT recommendation for
    interworking with full RFC 822 systems [Kille84b].
            original-sender     = "Original-Sender" ":" mailbox
    If an IPM has no IPMS.Heading.authorizing-users component and
    IPMS.Heading.originator.formal-name is different from
    MTS.OtherMessageDeliveryFields.originator-name, map
    MTS.OtherMessageDeliveryFields.originator-name, onto the Sender:
    field.
    If an IPM has a IPMS.Heading.authorizing-users component, and
    IPMS.Heading.originator.formal-name is different from
    MTS.OtherMessageDeliveryFields.originator-name,
    MTS.OtherMessageDeliveryFields.originator-name is mapped onto the
    Sender: field, and IPMS.Heading.originator mapped onto the
    Original-Sender: field.
    In other cases the MTS.OtherMessageDeliveryFields.originator-name,
    is already correctly represented.

Appendix C - Mappings specific to UUCP Mail

 Gatewaying of UUCP and X.400 is handled by first gatewaying the UUCP
 address into RFC 822 syntax (using RFC 976) and then gatewaying the
 resulting RFC 822 address into X.400.  For example, an X.400 address
         Country         US
         Organisation    Xerox
         Personal Name   John Smith
 might be expressed from UUCP as
         inthop!gate!gatehost.COM!/C=US/O=Xerox/PN=John.Smith/
 (assuming gate is a UUCP-ARPA gateway and gatehost.COM is an ARPA-
 X.400 gateway) or
         inthop!gate!Xerox.COM!John.Smith
 (assuming that Xerox.COM and /C=US/O=Xerox/ are equivalent.)
 In the other direction, a UUCP address Smith@ATT.COM, integrated into
 822, would be handled as any other 822 address.  A non-integrated
 address such as inthop!dest!user might be handled through a pair of
 gateways:

Hardcastle-Kille [Page 93] RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992

         Country         US
         ADMD            ATT
         PRMD            ARPA
         Organisation    GateOrg
         RFC-822         inthop!dest!user@gatehost.COM
 or through a single X.400 to UUCP gateway:
         Country         US
         ADMD            ATT
         PRMD            UUCP
         Organisation    GateOrg
         RFC-822         inthop!dest!user

Appendix D - Object Identifier Assignment

 An object identifier is needed for the extension IPMS element.  The
 following value shall be used.
 rfc-987-88 OBJECT IDENTIFIER ::=
     {ccitt data(9) pss(2342) ucl(234219200300) rfc-987-88(200)}
 id-rfc-822-field-list OBJECT IDENTIFIER ::= {rfc987-88 field(1)}

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 ")"

Hardcastle-Kille [Page 94] RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992

      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 "-">
      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
      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)
      encoded-pn      = [ given "." ] *( initial "." ) surname
      given           = 2*<ps-char not including ".">
      initial         = ALPHA
      surname         = printablestring
      std-or-address  = 1*( "/" attribute "=" value ) "/"
      attribute       = standard-type
                      / "RFC-822"
                      / registered-dd-type

Hardcastle-Kille [Page 95] RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992

                      / dd-key "." std-printablestring
      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        = "$" ps-char
      dmn-or-address  = dmn-part *( "." dmn-part )
      dmn-part        = attribute "$" value
      attribute       = standard-type
                      / "~" dmn-printablestring
      value           = dmn-printablestring
                      / "@"
      dmn-printablestring =
                      = *( dmn-char / dmn-pair )
      dmn-char        = <"{", "}", "*", and any ps-char
                                              except ".">
      dmn-pair        = "\."
      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
      md-and-mta       = [ "mta" mta "in" ]  global-id
      mta              = word
      arrival-time     = date-time

Hardcastle-Kille [Page 96] RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992

      md-or-mta        = "MD" global-id
                       / "MTA" mta
      Action-list      = 1#action
      action           = "Redirected"
                       / "Expanded"
                       / "Relayed"
                       / "Rerouted"
      dr-body-format = dr-summary <CRLF>
                      dr-recipients <CRLF>
                      dr-administrator-info-envelope <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
      dr-administrator-info-envelope = 3*( "*" text <CRLF> )
      dr-administrator-info =
       "**** The following information is directed towards"
       "the local administrator" <CRLF>
       "**** and is not intended for the end user" <CRLF> <CRLF>
       "DR generated by:" report-point <CRLF>
       "at" date-time <CRLF> <CRLF>
       "Converted to RFC 822 at" mta <CRLF>
       "at" date-time <CRLF> <CRLF>

Hardcastle-Kille [Page 97] RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992

       "Delivery Report Contents:" <CRLF> <CRLF>
       drc-field-list <CRLF>
       "***** End of administration information"
      drc-field-list       = *(drc-field <CRLF>)
      drc-field = "Subject-Submision-Identifier" ":"
                                      mts-msg-id
                / "Content-Identifier" ":" printablestring
                / "Content-Type" ":" mts-content-type
                / "Original-Encoded-Information-Types" ":"
                              encoded-info
                / "Originator-and-DL-Expansion-History" ":"
                              dl-history
                / "Reporting-DL-Name" ":" mailbox
                / "Content-Correlator" ":" content-correlator
                / "Recipient-Info" ":" recipient-info
                / "Subject-Intermediate-Trace-Information" ":"
                                        x400-trace
      recipient-info  = mailbox "," std-or ";"
                  report-type
                  [ "converted eits" encoded-info ";" ]
                  [ "originally intended recipient"
                          mailbox "," std-or ";" ]
                  [ "last trace" [ encoded-info ] date-time ";" ]
                  [ "supplementary info" <"> printablestring <"> ";" ]
                  [ "redirection history" 1#redirection ";"
                  [ "physical forwarding address"
                                        printablestring ";" ]
      report-type     = "SUCCESS" drc-success
                      / "FAILURE" drc-failure
      drc-success     = "delivered at" date-time ";"
                      [ "type of MTS user" labelled-integer ";" ]
      drc-failure     = "reason" labelled-integer ";"
                      [ "diagnostic" labelled-integer ";" ]
      report-point = [ "mta" word "in" ] global-id
      content-correlator = *word
      dl-history = 1#( mailbox "(" date-time ")")

Hardcastle-Kille [Page 98] RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992

      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#( oid / labelled-integer )
      prohibition     = "Prohibited" / "Allowed"
      mts-msg-id       = "[" global-id ";" *text "]"
      mts-content-type = "P2" /  labelled-integer
                      / object-identifer
      priority        = "normal" / "non-urgent" / "urgent"
      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

Hardcastle-Kille [Page 99] RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992

      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:"
                        <CRLF> <CRLF> message
      preferred-recipient = mailbox
      receipt-time        = date-time
      auto-comment        = printablestring
      ipn-suppl           = printablestring
      discard-reason     = "Expired" / "Obsoleted" /
                              "User Subscription Terminated"
      acknowledgement-mode = "Manually" / "Automatically"
      ipms-field = "Obsoletes" ":" 1#msg-id
                 / "Expiry-Date" ":" date-time
                 / "Reply-By" ":" date-time
                 / "Importance" ":" importance
                 / "Sensitivity" ":" sensitivity
                 / "Autoforwarded" ":" boolean
                 / "Incomplete-Copy" ":"
                 / "Language" ":" language
                 / "Message-Type" ":" message-type
                 / "Discarded-X400-IPMS-Extensions" ":" 1#oid
      importance      = "low" / "normal" / "high"
      sensitivity     = "Personal" / "Private" /
                             "Company-Confidential"
      language        = 2*ALPHA [ language-description ]

Hardcastle-Kille [Page 100] RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992

      language-description = printable-string
      message-type    = "Delivery Report"
                      / "InterPersonal Notification"
                      / "Multiple Part"
      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"
      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

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

Hardcastle-Kille [Page 101] RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992

    All gateways conforming to this specification shall have access to
    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.  Other
    standardised mechanisms to distribute the mapping information are
    expected.  In particular, mechanisms for using the Domain Name
    Scheme, and X.500 are planned.
    The definition of  global mapping information is being co-
    ordinated by the COSINE-MHS project, on behalf of the Internet and
    other X.400 and RFC 822 users.  For information on accessing this
    information contact:
         COSINE MHS Project Team
         SWITCH
         Weinbergstrasse 18
         8001 Zuerich
         Switzerland
         tel: +41 1 262 3143
         fax: +41 1 262 3151
         email:
         C=ch;ADMD=arcom;PRMD=switch;O=switch;OU=cosine-mhs;
         S=project-team
         or
         project-team@cosine-mhs.switch.ch
 2.  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.

Hardcastle-Kille [Page 102] RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992

    This syntax is not intended to be handled by users.
            dmn-or-address  = dmn-part *( "." dmn-part )
            dmn-part        = attribute "$" value
            attribute       = standard-type
                            / "~" dmn-printablestring
            value           = dmn-printablestring
                            / "@"
            dmn-printablestring =
                            = *( dmn-char / dmn-pair )
            dmn-char        = <"{", "}", "*", and any ps-char
                                                    except ".">
            dmn-pair        = "\."
    An example usage:
            ~ROLE$Big\.Chief.ADMD$ATT.C$US
            PRMD$DEC.ADMD$@.C$US
    The first example illustrates quoting of a ".", and the second
    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.
 3.  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:
            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:.

Hardcastle-Kille [Page 103] RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992

 4.  Domain -> O/R Address format
    The BNF is:
            domain-syntax "#" dmn-or-address "#"
    Note that the trailing "#" is used for clarity, as the dmn-or-
    address syntax might lead to values with trailing blanks.  Lines
    staring 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.
 5.  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 missing
    components in the hierarchy.  Use of this mapping is described in
    Section 4.3.2.
 6.  Domain -> O/R Address of Gateway table
    This uses the same format as the domain -> O/R address mapping.
    In this case, the two restrictions (omitted components and
    restrictions on components) do not apply.  Use of this mapping is
    described in Section 4.3.4.

Hardcastle-Kille [Page 104] RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992

Appendix G - Mapping with X.400(1984)

 This appendix defines modification 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 is mapped into a
 single IA5 body part, which is the 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.
 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:
  1. Only the 84/88 attributes identified in the table in

Section 4.2 are present.

  1. 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 are
 deprecated (the attribute should be omitted), and should 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 [Hardcastle-K92].

Hardcastle-Kille [Page 105] RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992

Appendix H - 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 acccess 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.

Appendix I - 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.  In
 particular:
  1. Formats for all fields shall be followed.
  1. 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.
  1. RFC 1137 shall not be followed when mapping to SMTP or to

JNT Mail

  1. All mappings of trace shall be implemented.
  1. There must be a mechanism to access all three global

mappings.

 A gateway should specify:

Hardcastle-Kille [Page 106] RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992

  1. Which 822-MTS protocols are supported. The relevant

appendices must be followed to claim support of a given

      protocol: SMTP (A); JNT Mail (B); UUCP (C).
  1. Which X.400 versions are supported (84 and/or 88).
  1. 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.
  1. The approach taken when upper bounds are exceeded at the IPM

level (5.1.3)

  1. The approach taken to return of contents (5.2)
  1. The approach taken to body parts which cannot be converted

(5.3.4)

  1. The approach taken to multiple copies vs non-disclosure

(4.6.2.2)

 The following are optional parts of this specification.  A conforming
 implementation should specify which of these it supports.
  1. 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.
  1. Support for the extension mappings of Appendix H.
  1. Support for returning illegal format content in a delivery

report

  1. Which address interpretation heuristics are supported

(4.3.4.1)

  1. If RFC 987 generated message ids are handled in a backwards

compatible manner (4.7.3.6)

Appendix J - 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

Hardcastle-Kille [Page 107] RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992

 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
  1. The new service elements of X.400 are dealt with.
  1. A clear distinction is made between origination and

reception

 3.  Basic Mappings
  1. Add teletex support
  1. Add object identifier support
  1. Add labelled integer support
  1. Make PrintableString ↔ ASCII mapping reversible
  1. The printable string mapping is aligned to the NBS mapping

derived from RFC 987.

 4.  Addressing
  1. Support for new addressing attributes
  1. The message ID mapping is changed to not be table driven

Hardcastle-Kille [Page 108] RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992

 5.  Detailed Mappings
  1. Define extended IPM Header, and use instead of second body

part for RFC 822 extensions

  1. Realignment of element names
  1. New syntax for reports, simplifying the header and

introducing a mandatory body format (the RFC 987 header

         format was unusable)
  1. Drop complex autoforwarded mapping
  1. Add full mapping for IP Notifications, defining a body

format

  1. Adopt an MTS Identifier syntax in line with the O/R Address

syntax

  1. A new format for X400 Trace representation on the RFC 822

side

 6.  Appendices
  1. Move Appendix on restricted 822 mappings to a separate RFC
  1. Delete Phonenet and SMTP Appendixes

Appendix K - Change History: RFC 1148 to this Document

 1.  General
  1. The scope of the document was changed to cover X.400(1984),

and so obsolete RFC 987.

  1. Changes were made to allow usage to connect RFC 822 networks

using X.400

  1. Text was tightened to be clear about optional and mandatory

aspects

  1. A good deal of clarification
  1. A number of minor EBNF errors
  1. Better examples are given
  1. Further X.400 upper bounds are handled correctly

Hardcastle-Kille [Page 109] RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992

 2.  Basic Mappings
  1. The encoding of object identifier is changed slightly
 3.  Addressing
  1. A global mapping of domain to preferred gateway is

introduced.

  1. An overflow mechanism is defined for RFC 822 addresses of

greater than 128 bytes.

  1. Changes were made to improve compatability 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.
    +         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
  1. The format of the Subject: lines is defined.
  1. Illegal use (repetition) of the heading EXTENSION is

corrected, and a new object identifier assigned.

  1. The Delivery Report format is extensively revised in light

of operational experience.

  1. The handling of redirects is significantly changed, as the

previous mechanism did not work.

 5.  Appendices
  1. An SMTP appendix is added, allowing optional use of the VRFY

command to improve probe information.

  1. Handling of JNT Mail Acknowledge-To is changed slightly.
  1. A DDA JNT-MAIL is allowed on input.
  1. The format definitions of Appendix F are explained further,

and a third table definition added.

Hardcastle-Kille [Page 110] RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992

  1. An appendix on use with X.400(1984) is added.
  1. Optional extensions are defined to give RFC 822 access to

further X.400 facilities.

  1. An appendix on conformance is added.

References

    CCITT88a.
         CCITT, "CCITT Recommendations X.408," Message Handling
         Systems: Encoded Information Type Conversion Rules, December
         1988.
    CCITT/ISO88a.
         CCITT/ISO, "CCITT Recommendations X.400/ ISO IS 10021-1,"
         Message Handling: System and Service Overview , December
         1988.
    CCITT/ISO88b.
         CCITT/ISO, "CCITT Recommendations X.420/ ISO IS 10021-7,"
         Message Handling Systems: Interpersonal Messaging System,
         December 1988.
    CCITT/ISO88c.
         CCITT/ISO, "CCITT Recommendations X.411/ ISO IS 10021-4,"
         Message Handling Systems: Message Transfer System: Abstract
         Service Definition and Procedures, December 1988.
    CCITT/ISO88d.
         CCITT/ISO, "Specification of Abstract Syntax Notation One
         (ASN.1)," CCITT Recommendation X.208 / ISO IS 8824, December
         1988.
    CCITT/ISO91a.
         CCITT/ISO, "Representation of O/R Addresses for Human
         Usage," PDAM to CCITT X.401 / ISO/IEC 10021-2, February
         1991.
    Crocker82a.
         Crocker, D., "Standard of the Format of ARPA Internet Text
         Messages," RFC 822, UDEL, August 1982.
    Hardcastle-K92.
         Hardcastle-Kille, S., "X.400 1988 to 1984 downgrading," RFC
         1328, UCL, May 1992.

Hardcastle-Kille [Page 111] RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992

    Horton86a.
         Horton, M., "UUCP Mail Interchange Format Standard," RFC
         976, February 1986.
    Kille84b.
         Kille, S., "Gatewaying between RFC 822 and JNT Mail," JNT
         Mailgroup Note 15, May 1984.
    Kille84a.
         Kille, S., (Editor), JNT Mail Protocol (revision 1.0), Joint
         Network Team, Rutherford Appleton Laboratory, March 1984.
    Kille86a.
         Kille, S., "Mapping Between X.400 and RFC 822," UK Academic
         Community Report (MG.19) / RFC 987, June 1986.
    Kille87a.
         Kille, S., "Addendum to RFC 987," UK Academic Community
         Report (MG.23) / RFC 1026, August 1987.
    Kille89a.
         Kille, S., "A String Encoding of Presentation Address," UCL
         Research Note 89/14, March 1989.
    Kille89b.
         Kille, S., "Mapping between full RFC 822 and RFC 822 with
         restricted encoding," RFC 1137, October 1989.
    Kille90a.
         Kille, S., "Mapping Between X.400(1988) / ISO 10021 and RFC
         822," RFC 1148, March 1990.
    Larmouth83a.
         Larmouth, J., "JNT Name Registration Technical Guide,"
         Salford University Computer Centre, April 1983.
    Postel84a.
         Postel J., and J. Reynolds, "Domain Requirements," RFC 920,
         USC/Information Sciences Institute, October 1984.
    Postel82a.
         Postel, J., "Simple Mail Transfer Protocol", RFC 821,
         USC/Information Sciences Institute, August 1982.
    Rose85a.
         Rose M., and E. Stefferud, "Proposed Standard for Message
         Encapsulation," RFC 934, January 1985.

Hardcastle-Kille [Page 112] RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992

    Systems85a.
         CEN/CENELEC/Information Technology/Working Group on Private
         Message Handling Systems, "FUNCTIONAL STANDARD A/3222,"
         CEN/CLC/IT/WG/PMHS N 17, October 1985.

SECURITY CONSIDERATIONS

 Security issues are not discussed in this memo.

AUTHOR'S ADDRESS

 Steve Hardcastle-Kille
 Department of Computer Science
 University College London
 Gower Street
 WC1E 6BT
 England
 Phone: +44-71-380-7294
 EMail: S.Kille@CS.UCL.AC.UK

Hardcastle-Kille [Page 113]

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