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rfc:rfc1138

Network Working Group S. Kille Request for Comments 1138 University College London Updates: RFCs 822, 987, 1026 December 1989

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

Status of this Memo

 This RFC suggests an electronic mail protocol mapping for the
 Internet community and UK Academic Community, and requests discussion
 and suggestions for improvements.  This memo does not specify an
 Internet standard.  Distribution of this memo is unlimited.
 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 based on RFC 987 and RFC 1026 [Kille86a, Kille87a],
 which define a similar mapping for X.400 (1984).  This document does
 not obsolete the earlier ones, as its domain of application is
 different.

Specification

 This document specifies a mapping between two protocols.  This
 specification should be used when this mapping is performed on the
 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 ...............................................    2
 1.1  X.400 .................................................    2
 1.2  RFC 822 ...............................................    3
 1.3  The need for conversion ...............................    4
 1.4  General approach ......................................    4
 1.5  Gatewaying Model ......................................    5
 1.6  RFC 987 ...............................................    7
 1.7  Aspects not covered ...................................    8
 1.8  Subsetting ............................................    9
 1.9  Document Structure ....................................    9

Kille [Page 1] RFC 1138 Mapping X.400(88) and 822 December 1989

 1.10  Acknowledgements .....................................   10
 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 .........................................   25
 3.3  Standard Types ........................................   25
 3.4  Encoding ASCII in Printable String ....................   28
 4.  Addressing .............................................   29
 4.1  A textual representation of MTS.ORAddress .............   30
 4.2  Basic Representation ..................................   30
 4.3  EBNF.822-address <-> MTS.ORAddress ....................   34
 4.4  Repeated Mappings .....................................   43
 4.5  Directory Names .......................................   45
 4.6  MTS Mappings ..........................................   45
 4.7  IPMS Mappings ....... .................................   48
 5.  Detailed Mappings ......................................   52
 5.1  RFC 822 -> X.400 ......................................   52
 5.2  Return of Contents ....................................   59
 5.3  X.400 -> RFC 822 ......................................   60
 Appendix A  Differences with RFC 987 .......................   78
 1.  Introduction ...........................................   78
 2.  Service Elements .......................................   78
 3.  Basic Mappings .........................................   78
 4.  Addressing .............................................   78
 5.  Detailed Mappings ......................................   79
 6.  Appendices .............................................   79
 Appendix B  Mappings specific to the JNT Mail ..............   79
 1.  Introduction ...........................................   79
 2.  Domain Ordering ........................................   79
 3.  Acknowledge-To: ........................................   79
 4.  Trace ..................................................   80
 5.  Timezone specification .................................   80
 6.  Lack of 822-MTS originator specification ...............   80
 Appendix C  Mappings specific to UUCP Mail .................   81
 Appendix D  Object Identifier Assignment ...................   82
 Appendix E  BNF Summary ....................................   82
 Appendix F  Format of address mapping tables ...............   89
 References .................................................   91

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

Kille [Page 2] RFC 1138 Mapping X.400(88) and 822 December 1989

 (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 is the current specification of the messaging standard on the
 Internet.  This standard evolved with the evolution of the network
 from the ARPANET (created by the Defense Advanced Research Projects
 Agency) to the Internet, which now involves over 1000 networks and is
 sponsored by DARPA, NSF, DOE, NASA, and NIH.  It specifies an end to
 end message format.  It is used in conjunction with a number of
 different message transfer protocol environments.
    SMTP Networks
       On the 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 1034
       which is a Specification for domains and a distributed name
       service [Mockapetris87a].
    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 1034, but not the corresponding domain nameservers
       [Horton86a].
    Csnet
       Some portions of Csnet follow the Internet protocols.  The
       dialup portion of Csnet uses the Phonenet protocols as a
       replacement for RFC 821.  This portion uses domains which
       conform to RFC 1034, but not the corresponding domain
       nameservers.
    Bitnet
       Some parts of Bitnet and related networks use RFC 822 related
       protocols, with EBCDIC encoding.

Kille [Page 3] RFC 1138 Mapping X.400(88) and 822 December 1989

    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.
    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

Kille [Page 4] RFC 1138 Mapping X.400(88) and 822 December 1989

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

Kille [Page 5] RFC 1138 Mapping X.400(88) and 822 December 1989

 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 define 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
 or MTA Service Elements.

Kille [Page 6] RFC 1138 Mapping X.400(88) and 822 December 1989

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 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).
 In particular, there is no expectation of additional X.400 services
 being mapped - although this may be possible in some cases.

1.6. RFC 987

 Much of this work is based on the initial specification of RFC 987
 and in its addendum RFC 1026.  A basic decision is that the mapping
 will be to the full 1988 version of X.400, and not to a 1984
 compatible subset.  This is important, to give good support to
 communities which will utilise full X.400 at an early date.  This has

Kille [Page 7] RFC 1138 Mapping X.400(88) and 822 December 1989

 the following implications:
  1. This document does not obsolete RFC 987, as it has a

different domain of application.

  1. If a gatewayed message is being transferred to a 1984

system, then RFC 987 should be used. If the X.400 side of

         the gateway is a 1988 system, then it should be operated in
         1984 compatibility mode.  There is no advantage and some
         disadvantage in using the new mapping, and later on applying
         X.400 downgrading rules.  Note that 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.
  1. New features of X.400 can be used to provide a much cleaner

mapping than that defined in 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.
 A summary of changes made is given in Appendix A.

1.7. 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
 These are really coupled.  To map the X.400 services, this
 specification defines a number of extensions to RFC 822.  As a side
 effect, these give the 822 user access to SOME X.400 services.
 However, the aim on the RFC 822 side is to preserve current service,
 and it is intentional that access is not given to all X.400 services.
 Thus, it will be a poor choice for X.400 implementors to use RFC
 987(88) as an interface - there are too many aspects of X.400 which

Kille [Page 8] RFC 1138 Mapping X.400(88) and 822 December 1989

 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.

1.8. 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.

1.9. 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 six appendices:
    A.   Differences with RFC 987
    B.   Mappings Specific to JNT Mail
    C.   Mappings Specific to UUCP Mail
    D.   Object Identifier Assignment
    E.   BNF Summary
    F.   Format of Address Tables
 WARNING:
    THE REMAINDER OF THIS SPECIFICATION IS TECHNICALLY DETAILED.

Kille [Page 9] RFC 1138 Mapping X.400(88) and 822 December 1989

    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.

1.10. Acknowledgements

 This work was partly sponsored by the Joint Network Team.  The
 workshop at UCL in June 1989 to work on this specification was also
 an IFIP WG 6.5 meeting.
 The work in this specification was substantially based on RFC 987,
 which had input from many people.
 Useful comments and suggestions were made by Pete Cowen (Nottingham
 Univ), Jim Craigie (JNT), Christian Huitema (Inria), Peter Lynch
 (Prime), Julian Onions (Nottingham Univ), Sandy Shaw (Edinburgh
 Univ), Einar Stefferud (NMA), and Peter Sylvester (GMD).

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.

Kille [Page 10] RFC 1138 Mapping X.400(88) and 822 December 1989

    Not Supported
       The service cannot be provided, as there is a complete
       mismatch.
    Partial Support
       The service can be partially fulfilled.
 In the first two cases, the service is simply marked as "Supported"
 or "Not Supported".  Some explanation may be given if there are
 additional implications, or the (non) support is not intuitive.  For
 partial support, the level of partial support is 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.
 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

Kille [Page 11] RFC 1138 Mapping X.400(88) and 822 December 1989

 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).
 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
 should 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.

Kille [Page 12] RFC 1138 Mapping X.400(88) and 822 December 1989

    Subject:
         Supported.
    Comments:
         Supported by use of an extra body part.
    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:

Kille [Page 13] RFC 1138 Mapping X.400(88) and 822 December 1989

    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):
    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:
    Redirection-History:
    Reply-By:
    Requested-Delivery-Method:

Kille [Page 14] RFC 1138 Mapping X.400(88) and 822 December 1989

    Sensitivity:
    X400-Content-Type:
    X400-MTS-Identifier:
    X400-Originator:
    X400-Received:
    X400-Recipients:

2.3. X.400

2.3.1. Origination in X.400

 When mapping services from X.400 to RFC 822 which are not supported
 by RFC 822, new RFC 822 headers are defined.  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).

Kille [Page 15] RFC 1138 Mapping X.400(88) and 822 December 1989

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

2.3.1.1. Basic Interpersonal Messaging Service

 These are the mandatory IPM services as listed in Section 19.8 of
 X.400 / ISO/IEC 10021-1, listed here in the order given.  Section
 19.8 has cross references to short definitions of each service.
    Access management
         N/A (local).
    Content Type Indication
         Supported by a new RFC 822 header (Content-Type:).
    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.

Kille [Page 16] RFC 1138 Mapping X.400(88) and 822 December 1989

    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
         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

Kille [Page 17] RFC 1138 Mapping X.400(88) and 822 December 1989

         cases it will not be possible to map the body part in
         question.
    Content Confidentiality
         Not supported.
    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).

Kille [Page 18] RFC 1138 Mapping X.400(88) and 822 December 1989

    Disclosure of Other Recipients
         Supported by use of a new RFC 822 header (X400-Recipients:).
         This is descriptive information for the RFC 822 recipient,
         and is not reverse mappable.
    DL Expansion History Indication
         Supported by use of a new RFC 822 header
         (DL-Expansion-History:).
    DL Expansion Prohibited
         Distribution List means MTS supported distribution list, in
         the manner of X.400.  This service does not exist in the RFC
         822 world.  RFC 822 distribution lists should be regarded 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:)

Kille [Page 19] RFC 1138 Mapping X.400(88) and 822 December 1989

          is provided, which may be used by the recipient.
    Message Flow Confidentiality
          Not supported.
    Message Origin Authentication
          N/A (reception).
    Message Security Labelling
          Not supported.
    Message Sequence Integrity
          Not supported.
    Multi-Destination Delivery
          Supported.
    Multi-part Body
          Supported, 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).

Kille [Page 20] RFC 1138 Mapping X.400(88) and 822 December 1989

    Physical Delivery Notification by PDS
          N/A (PDAU).
    Physical Forwarding Allowed
          Supported by use of a comment in a new RFC 822 header
          (X400-Recipients:), associated with the recipient in
          question.
    Physical Forwarding Prohibited
          Supported by use of a comment in a new RFC 822 header
          (X400-Recipients:), associated with the recipient in
          question.
    Prevention of Non-delivery notification
          Supported, 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.

Kille [Page 21] RFC 1138 Mapping X.400(88) and 822 December 1989

    Registered Mail
          N/A (PDAU).
    Registered Mail to Addressee in Person
          N/A (PDAU).
    Reply Request Indication
          Supported as comment next to address.
    Replying IP Message Indication
          Supported.
    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).

Kille [Page 22] RFC 1138 Mapping X.400(88) and 822 December 1989

    Subject Indication
          Supported.
    Undeliverable Mail with Return of Physical Message
          N/A (PDAU).
    Use of Distribution List
          In principle this applies only to X.400 supported
          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 may be 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 may be 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

Kille [Page 23] RFC 1138 Mapping X.400(88) and 822 December 1989

    Primary and Copy Recipients Indication
    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 should 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.bilateral-info).
    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.

Kille [Page 24] RFC 1138 Mapping X.400(88) and 822 December 1989

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].

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

Kille [Page 25] RFC 1138 Mapping X.400(88) and 822 December 1989

 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 should be 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) should be used [CCITT/ISO88a].
 These will then be encoded in ASCII.
 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

Kille [Page 26] RFC 1138 Mapping X.400(88) and 822 December 1989

 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.
 The UTCTime format which specifies the timezone offset should be
 used.

3.3.6. Integer

 A basic ASN.1 Integer will be mapped onto EBNF.numericstring.  In many
 cases ASN.1 will enumerate Integer values or use ENUMERATED.  An EBNF
 encoding labelled-integer is provided. When mapping from EBNF to
 ASN.1, only the integer value is mapped, and the associated text is
 discarded.  When mapping from ASN.1 to EBNF, addition of an
 appropriate text label is strongly encouraged.
    labelled-integer ::= [ key-string ] "(" numericstring ")"
    key-string      = *key-char
    key-char        = <a-z, A-Z, 1-9, and "-">

3.3.7. Object Identifier

 Object identifiers are represented in a form similar to that
 given in ASN.1.  The numbers are mandatory, to ease encoding.
 It is recommended that as many strings as possible are used, to
 facilitate user recognition.
    object-identifier ::= [ defined-value ] oid-comp-list

Kille [Page 27] RFC 1138 Mapping X.400(88) and 822 December 1989

    oid-comp-list ::= oid-comp oid-comp-list
                    | oid-comp
    defined-value ::= key-string
    oid-comp ::= [ key-string ] "(" numericstring ")"

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 can
 be used to encode ASCII in the PrintableString character set.
    ps-encoded       = *( ps-restricted-char / ps-encoded-char )
    ps-encoded-char  = "(a)"               ; (@)
                     / "(p)"               ; (%)
                     / "(b)"               ; (!)
                     / "(q)"               ; (")
                     / "(u)"               ; (_)
                     / "(l)"               ; "("
                     / "(r)"               ; ")"
                     / "(" 3DIGIT ")"
 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 should be
 mapped in a case insensitive manner, but always be 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.

Kille [Page 28] RFC 1138 Mapping X.400(88) and 822 December 1989

 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 should be given to the
 procedure doing the mapping. In some cases, it may be preferable to
 pass the printable string through unaltered.
 Some examples are now given.  Note the arrows which indicate
 asymmetrical mappings:
                 PrintableString           ASCII
                 'a demo.'         <->   'a demo.'
                 foo(a)bar         <->   foo@bar
                 (q)(u)(p)(q)      <->   "_%"
                 (a)               <->   @
                 (A)               <->   @
                 (l)a(r)           <->   (a)
                 (126)             <->   ~
                 (                  ->   (
                 (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 should be
 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

Kille [Page 29] RFC 1138 Mapping X.400(88) and 822 December 1989

 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 aspects should be encoded, in order to guarantee
 return of error messages, and to optimise third party replies.

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 N 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

Kille [Page 30] RFC 1138 Mapping X.400(88) and 822 December 1989

88 Attributes

MTS.CommonName CN P/T 18.3.2 1 MTS.TeletexCommonName CN P/T 18.3.2 2 MTS.TeletexOrganizationName O P/T 18.3.9 3 MTS.TeletexPersonalName PN P/T 18.3.12 4 MTS.TeletexPersonalName.surname S P/T 18.3.12 4 MTS.TeletexPersonalName.given-name G P/T 18.3.12 4 MTS.TeletexPersonalName.initials I P/T 18.3.12 4 MTS.TeletexPersonalName

 .generation-qualifier            GQ             P/T     18.3.12   4

MTS.TeletexOrganizationalUnitNames

 .value                           OU             P/T     18.3.10   5

MTS.TeletexDomainDefinedAttribute

 .value                           DD             P/T     18.1      6

MTS.PDSName PD-SYSTEM P 18.3.11 7 MTS.PhysicalDeliveryCountryName PD-C P 18.3.13 8 MTS.PostalCode POSTCODE 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-D P/T 18.3.4 12 MTS.PhysicalDeliveryPersonName PD-PN P/T 18.3.17 13 MTS.PhysicalDelivery PD-O P/T 18.3.16 14

 OrganizationName

MTS.ExtensionPhysicalDelivery

 AddressComponents                PD-EXT-LOC     P/T     18.3.5   15

MTS.UnformattedPostalAddress PD-ADDRESS P/T 18.3.25 16 MTS.StreetAddress STREET P/T 18.3.22 17 MTS.PostOfficeBoxAddress PO-BOX P/T 18.3.18 18 MTS.PosteRestanteAddress POSTE-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 NET-TTYPE 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

Kille [Page 31] RFC 1138 Mapping X.400(88) and 822 December 1989

               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 should be mapped into the BNF.
 When generating ASN.1, the NumericString encoding should 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,
 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.

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.   If Surname contains full stop, then it may not be in the
         first two characters, and either initials or given name is
         present.
 The following EBNF is defined:
              encoded-pn      = [ given "." ] *( initial "." ) surname
              given           = 2*<ps-char not including ".">

Kille [Page 32] RFC 1138 Mapping X.400(88) and 822 December 1989

              initial         = ALPHA
              surname         = printablestring
 This can be used to map from any string containing only printable
 string characters to an O/R address personal name. 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.
 For an O/R address which follows the above restrictions, a string can
 be 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 proposed 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.
              std-or-address  = 1*( "/" attribute "=" value ) "/"
              attribute       = standard-type
                              / "RFC-822"
                              / registered-dd-type
                              / dd-key "." std-printablestring
              standard-type   = key-string

Kille [Page 33] RFC 1138 Mapping X.400(88) and 822 December 1989

              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 value, after quote removal, should be
 interpreted according to the defined encoding.
 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 should be interpreted according to the syntax implied from
 the encoding, and aligned to either the teletex or printable string
 form.  Key and value should 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 should be done in a case- independent
 manner.
 If the value is registered-dd-type, the value is registered with the
 IANA and will be listed in the Assigned Numbers RFC, then the value
 should be interpreted 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.

Kille [Page 34] RFC 1138 Mapping X.400(88) and 822 December 1989

    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.  Further O/R Address
 information may be associated with the 822.domain component.  This
 cannot be used in the general case, basically due to character set
 problems, and lack of order in X.400 O/R Addresses.  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.
 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)
 should be 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).
    This form of source routing is now discouraged in the Internet
    (Host Requirements, page 58 [Braden89a]).
 The 822.domain associated with the 822.local-part may also identify
 the gateway from within the RFC 822 world.  This final 822.domain may
 be used to determine some number of O/R Address attributes.  The
 following O/R Address attributes are considered 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.
    Associations may be 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"

Kille [Page 35] RFC 1138 Mapping X.400(88) and 822 December 1989

    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 should 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". It should be noted that
         attributes may have null values, and that this is treated
         separately from omitted attributes (whilst it would be bad
         practice to treat these two cases differently, they must be
         allowed for).
 This set of mappings need only be known by the gateways relaying
 between the RFC 822 world, and the O/R Address space associated with
 the mapping in question.  However, it is desirable (for the optimal
 mapping of third party addresses) for all gateways to know these
 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:

Kille [Page 36] RFC 1138 Mapping X.400(88) and 822 December 1989

              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 should be
 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, the encoding J.Linnimouth@Marketing.Widget.COM would
 result.
 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 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.

Kille [Page 37] RFC 1138 Mapping X.400(88) and 822 December 1989

    1.   In the context of RFC 822, and RFC 1034
         [Crocker82a, Mockapetris87a], the string can be used
         directly.
    2.   In the context of the JNT Mail protocol, and the NRS
         [Kille84a, Larmouth83a], the string should be interpreted
         according to Mailgroup Note 15 [Kille84b].
    3.   In the context of UUCP based systems, the string should 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"
 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.

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.

Kille [Page 38] RFC 1138 Mapping X.400(88) and 822 December 1989

 There are three places where an order must be 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:
  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.
         There will be some cases where an X.400 O/R address of this
         encoding will be generated by an end user from external
         information.  The ordering of attributes may be inverted or
         mixed.  For this reason, the following heuristics may be
         applied:
  1. If there is an Organisation attribute to the left of

any Org Unit attribute, assume that the hierarchy is

              inverted.
  1. If an inversion of the Org Unit hierarchy generates a

valid address, when the preferred order does not,

              assume that the hierarchy is inverted.
    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

Kille [Page 39] RFC 1138 Mapping X.400(88) and 822 December 1989

         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 should proceed as follows, by first assuming case 1).
 STAGE I.
 1.   If the 822-address is not of the form:
              local-part "@" domain
      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 a
      list of supported mappings (see Appendix F).  If this fails,
      and the EBNF.domain does not explicitly identify the local
      gateway, go to stage II.  If it succeeds, allocate the
      attributes associated with EBNF.known-domain, and
      systematically allocate the attributes implied by each

Kille [Page 40] RFC 1138 Mapping X.400(88) and 822 December 1989

      EBNF.domain-syntax component.  If the domain explicitly
      identifies the gateway, allocate no attributes.
 3.   If the local-part contains any characters not in
      PrintableString, go to stage II.
 4.   If the 822.local-part uses the 822.quoted-string encoding,
      remove this quoting.  Parse the (unquoted) 822.local-part
      according to the EBNF EBNF.std-or-address.  If this parse
      fails, parse the local-part according to the EBNF
      EBNF.encoded-pn.  The result is a set of type/value pairs.
      If the values generated conflict with those derived in step
      2 (e.g., a duplicated country attribute), the domain should
      be assumed to be an RFC 987 gateway.  In this case, take
      only the LHS derived attributes.  Otherwise add LHS and RHS
      derived attributes together.
 5.   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.
 6.   Ensure that the set of attributes conforms both to the
      MTS.ORAddress specification and to the restrictions on this
      set given in X.400.  If not go to stage II.
 7.   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.  If the address is an 822-MTS recipient
 address, it must be rejected, as there is a need to interpret
 such an address in X.400.  For the 822-MTS return address, and
 any addresses in the RFC 822 header, they should now be encoded
 as RFC 822 addresses in an X.400 O/R Name:
 1.   Convert the EBNF.822-address to PrintableString, as
      specified in Chapter 3.
 2.   The "RFC-822" domain defined attribute should be generated
      from this string.
 3.   Build the rest of the O/R Address in the local Management
      Domain agreed manner, so that the O/R Address will receive a
      correct global interpretation.
 Note that the domain defined attribute value has a maximum length

Kille [Page 41] RFC 1138 Mapping X.400(88) and 822 December 1989

 of MTS.ub-domain-defined-attribute-value-length (128).  If this
 is exceeded by a mapping at the MTS level, then the gateway
 should reject the message in question.  If this occurs at the
 IPMS level, then the action should depend on the policy being
 taken, which is discussed in Section 5.1.3.

4.3.5. X.400 → RFC 822

 There are two basic cases:
 1.   RFC 822 addresses encoded in X.400.
 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 a single "RFC-822" domain defined attribute
 present.  In this case, use mapping A.  For other O/R Addresses
 which:
 1.   Contain the special attribute.
      AND
 2.   Identifies the local gateway or any other known gateway with
      the other attributes.
 Use mapping A.  In 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.
 Mapping A
 1.   Map the domain defined attribute value to ASCII, as defined
      in Chapter 3.
 Mapping B
 This will be 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.

Kille [Page 42] RFC 1138 Mapping X.400(88) and 822 December 1989

 2.   Noting the hierarchy specified in 4.3.1, determine the
      maximum set of attributes which have an associated domain
      specification.  If no match is found, allocate the domain as
      the domain specification of the local gateway, and go to
      step 4.
 3.   Following the 4.3.1 hierarchy and noting any omitted
      components implied by the mapping tables (see Appendix F),
      if each successive component exists, and 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 should not be mapped onto subdomain, as
      822.local-part cannot be null.
 4.   If the remaining components are personal-name components,
      conforming to the restrictions of 4.2.1, then EBNF.encoded-
      pn should be derived to form 822.local-part.  In other cases
      the remaining components should simply be encoded as a
      822.local-part using the EBNF.std-or-address syntax.  If
      necessary, the 822.quoted-string encoding should be used.
      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

 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
 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

Kille [Page 43] RFC 1138 Mapping X.400(88) and 822 December 1989

 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
 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

Kille [Page 44] RFC 1138 Mapping X.400(88) and 822 December 1989

 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 should be 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.

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-
 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 should be made for each
 component of MTS.PerRecipientMessageSubmissionFields.
      recipient-name
           This should be derived from the 822-MTS recipient by the
           basic ORAddress mapping.

Kille [Page 45] RFC 1138 Mapping X.400(88) and 822 December 1989

      originator-report-request
           This should be set according to content return policy, as
           discussed in Section 5.2.
      explicit-conversion
           This optional component should be omitted, as this service
           is not needed.
      extensions
           The default value (no extensions) should be 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 should be present in
 these fields.  There may also be the need to generate a delivery
 report.

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 should be
 discarded.
 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 should be set to the same value as the

Kille [Page 46] RFC 1138 Mapping X.400(88) and 822 December 1989

 822-MTS originator.  In addition, if
 MTS.OtherMessageDeliveryFields.originator-name (MTS.ORName) contains
 MTS.ORName.directory-name then this Directory Name should be
 represented in an 822.comment.
 Recipient names, taken from each value of
 MTS.OtherMessageDeliveryFields.this-recipient-name and
 MTS.OtherMessageDeliveryFields.other-recipient-names should  be 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.  If any MTS.ORName.directory-name is
 present, it should be represented in an 822.comment.  If
 MTS.OtherMessageDeliveryFields.orignally-intended-recipient-name is
 present, then it should be represented in an associated 822.comment,
 starting with the string "Originally Intended Recipient".
 In addition, the following per-recipient services from
 MTS.OtherMessageDeliveryFields.extensions should be 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 may be chosen by
 the implementor.   If the parameter has a default value, then no
 comment should be inserted.
      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)".

Kille [Page 47] RFC 1138 Mapping X.400(88) and 822 December 1989

4.6.2.3. Delivery Report Generation

 If MTA.PerRecipientMessageTransferFields.per-recipient-indicators
 requires a positive delivery notification, this should be
 generated by the gateway.  Supplementary Information should be
 set to indicate that the report is gateway generated.

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 should be used to generate
 MTS.MTSIdentifier.global-domain-identifier.
 MTS.MTSIdentifier.local-identifier should be set to the
 822.msg-id, including the braces "<" and ">".  If this string is
 longer than MTS.ub-local-id-length (32), then it should be
 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.

4.7. IPMS Mappings

 All RFC 822 addresses are assumed to use the 822.mailbox syntax.
 This should include 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 should be built consisting of (if present):

Kille [Page 48] RFC 1138 Mapping X.400(88) and 822 December 1989

  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 should then be encoded into T.61 us a human
    oriented mapping (as described in Chapter 3).  If the string
    is not null, it should be assigned to
    IPMS.ORDescriptor.free-form-name.
    3.   IPMS.ORDescriptor.telephone-number should be omitted.
 If IPMS.ORDescriptor is being used in IPMS.RecipientSpecifier,
 IPMS.RecipientSpecifier.reply-request and
 IPMS.RecipientSpecifier.notification-requests should be set to
 default values (none and false).
 If the 822.group construct is present, any included 822.mailbox
 should be encoded as above to generate a separate IPMS.ORDescriptor.
 The 822.group should be 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
         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 should be added.
    3.   If IPMS.ORDescriptor.telephone-number is present, this
         should be placed in an 822.comment, with the string "Tel ".
         The normal international form of number should be used.  For
         example:
                (Tel +44-1-387-7050)

Kille [Page 49] RFC 1138 Mapping X.400(88) and 822 December 1989

    4.   If IPMS.ORDescriptor.formal-name.directory-name is present,
         then a text representation should be 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)" should be appended to the
         address.  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)" should be appended to the
         address.
 If IPMS.ORDescriptor.formal-name is absent, IPMS.ORDescriptor.free-
 form-name should be converted to ASCII, and used as 822.phrase within
 the RFC 822 822.group syntax.  For example:
    Free Form Name ":" ";"
 Steps 3-6 should then be followed.

4.7.3. IP Message IDs

 There is a need to map both ways between 822.msg-id and
 IPMS.IPMIdentifier.  This allows for X.400 Receipt Notifications,
 Replies, and Cross References to reference an RFC 822 Message ID,
 which is preferable to a gateway generated ID.  A reversible and
 symmetrical mapping is defined.  This 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).

Kille [Page 50] RFC 1138 Mapping X.400(88) and 822 December 1989

 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.

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>

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

Kille [Page 51] RFC 1138 Mapping X.400(88) and 822 December 1989

 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 "Reply-To:" and "References:", the encoding 822.phrase may be used
 as an alternative to 822.msg-id.  To map from 822.phrase to
 IPMS.IPMIdentifier, assign IPMS.IPMIdentifier.user-relative-
 identifier to the phrase.  When mapping from IPMS.IPMIdentifier for
 "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 proposed here is different to that used in RFC 987, as
 the RFC 987 mapping lead to changed message IDs in many cases.
 Fixing the problems is preferable to retaining backwards
 compatibility.  An implementation of this standard is encouraged to
 recognise message IDs generated by RFC 987.

Chapter 5 – Detailed Mappings

 This chapter gives 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.  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

Kille [Page 52] RFC 1138 Mapping X.400(88) and 822 December 1989

 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 RFC822Field
                      ::= id-rfc-822-field
              RFC822Field ::= IA5String
 The Object Identifier id-rfc-822-field is defined in Appendix D.
 To encode any RFC 822 Header using this extension, the RFC822Field
 should be set to the  822.field omitting the trailing CRLF (e.g.,
 "Fruit-Of-The-Day: Kiwi Fruit"). Structured fields should be
 unfolded.  There should be no space before the ":".  The reverse
 mapping builds the RFC 822 field in a straightforward manner.

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 should be
 encoded as content type 2.  Otherwise, it should be 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 may break some recipient UAs.
    2.   Reject any inbound message which would cause a message

Kille [Page 53] RFC 1138 Mapping X.400(88) and 822 December 1989

         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.
 These choices 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 should be
 generated by the gateway.  With the exception of "Received:", the
 values of multiple fields should be merged (e.g., If there are two
 "To:" fields, then the mailboxes of both should be used).
 Information should 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.

Kille [Page 54] RFC 1138 Mapping X.400(88) and 822 December 1989

      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 should 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 should be applied to
           RFC 822 fields where the content of the field does not
           conform to RFC 822 (e.g., a Date: field with unparsable
           syntax).

5.1.4. Mappings to the MTS Abstract Service

 The MTS.MessageSubmissionEnvelope comprises
 MTS.PerMessageSubmissionFields, and

Kille [Page 55] RFC 1138 Mapping X.400(88) and 822 December 1989

 MTS.PerRecipientMessageSubmissionFields.  The mandatory parameters
 should be 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 should be left out, and default components
 defaulted, with two exceptions.  For
 MTS.PerMessageSubmissionFields.per-message-indicators, the following
 settings should be made:
  1. Alternate recipient should be allowed, as it seems desirable

to maximise the opportunity for (reliable) delivery.

  1. Content return request should be set according to the issues

discussed in Section 5.2.

 MTS.PerMessageSubmissionFields.original-encoded-information-types
 should be made a set of one element
 BuiltInEncodedInformationTypes.ia5-text.
 The MTS.PerMessageSubmissionFields.content-correlator should be
 encoded as IA5String, and contain the Subject:, Message-ID:, Date:,
 and To: fields (if present).  This should include the strings
 "Subject:", "Date:", "To:", "Message-ID:", and appropriate folding.
 This should be truncated to MTS.ub-content-correlator-length (512)
 characters.  In addition, if there is a "Subject:" field, the
 MTS.PerMessageSubmissionFields.content-identifier, should be set to a
 printable string representation of the contents of it, truncated to
 MTS.ub-content-id-length (16).  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
 service, for the following reasons:
  1. So the the MTS Message Identifier can be generated from the

Kille [Page 56] RFC 1138 Mapping X.400(88) and 822 December 1989

      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 should be
      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
      should be 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
      should be generated in an analogous manner, although this
      may later be dropped (see the procedures for "Received:").
 Received:
      All RFC 822 trace is used to derive
      MTA.PerMessageTransferFields.trace-information and
      MTA.PerMessageTransferFields.internal-trace-information.
      Processing of Received: lines should follow processing of
      Date:, and should be done from the the bottom to the top of
      the RFC 822 header (i.e., in chronological order).  If other
      trace elements are processed (Via:, X400-Received:), care
      should be taken to keep the relative ordering correct.  The

Kille [Page 57] RFC 1138 Mapping X.400(88) and 822 December 1989

      initial element of
      MTA.PerMessageTransferFields.trace-information will be
      generated already (from Date:).
      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 should 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
      should be set to the value derived.  The
      MTA.InternalTraceInformationElement.mta-supplied-information
      (MTA.MTASuppliedInformation) should be 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 should be
      taken from the "by" component of the "Received:" field,
      truncated to MTS.ub-mta-name-length (32).  For example:
         Received: from computer-science.nottingham.ac.uk by
            vs6.Cs.Ucl.AC.UK via Janet with NIFTP  id aa03794;
            28 Mar 89 16:38 GMT
 Generates the string:
         vs6.Cs.Ucl.AC.UK
 Note that before transferring the message to some ADMDs, additional
 trace stripping may be required, as the implied path through multiple

Kille [Page 58] RFC 1138 Mapping X.400(88) and 822 December 1989

 MDs would violate ADMD policy.
 Two extended fields must be mapped, in order to prevent looping.
 "DL-Expansion-History:" is mapped to
 MTA.PerMessageTransferFields.extensions.dl-expansion-history.
 "Redirection-History:" is mapped to
 MTA.PerRecipientMessageTransferFields.extensions.redirection-history.

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 these fields to X.400, with the
 exception of "DL-Expansion-History" and "Redirection-History"
 described in the previous section.  However, it is usually desirable
 and beneficial to do so, particularly to facilitate support of a
 message traversing multiple gateways.  These mappings may be onto
 MTA, MTS, or IPMS services.

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 should 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.

Kille [Page 59] RFC 1138 Mapping X.400(88) and 822 December 1989

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
 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 should 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 should be assigned.
 Date:
      A value will always be generated
 From:If this is not generated by the mapping, it should be
      assigned equal to the 822-MTS Originator.  If this is
      gateway generated, an appropriate 822.phrase should be
      added.
 At least one recipient field
      If no recipient fields are generated, a field "To: list:;",
      should be added.
 This will ensure minimal RFC 822 compliance.  When generating RFC
 822 headers, folding should be used in an appropriate manner.

Kille [Page 60] RFC 1138 Mapping X.400(88) and 822 December 1989

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)
                              / "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

Kille [Page 61] RFC 1138 Mapping X.400(88) and 822 December 1989

                         / "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 ]
              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).
 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:".

Kille [Page 62] RFC 1138 Mapping X.400(88) and 822 December 1989

 IPMS.Heading.obsoleted-IPMs
      Mapped to the extended RFC 822 field "Obsoletes:"
 IPMS.Heading.related-IPMs
      Mapped to "References:".
 IPMS.Heading.subject
      Mapped to "Subject:".  The contents are converted to ASCII
      (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. If possible, the language-description
      should be filled in with a human readable description of the
      language.
 If the RFC 822 extended header is found, this should be mapped onto
 an RFC 822 header, as described in Section 5.1.2.
 If a non-standard extension is found, it should be discarded, unless
 the gateway understands the extension and can perform an appropriate
 mapping onto an RFC 822 header field.  If extensions are discarded,

Kille [Page 63] RFC 1138 Mapping X.400(88) and 822 December 1989

 the list should be 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:
 IPMS.IA5Text
      The mapping is straightforward (see Chapter 3).
 IPMS.MessageBodyPart
      The X.400 -> RFC 822 mapping  should be recursively applied,
      to generate an RFC 822 Message.  If present, the
      IPMS.MessageBodyPart.parameters.delivery-envelope should be
      used for the MTS Abstract Service Mappings.  If present, the
      IPMS.MessageBodyPart.parameters.delivery-time should be
      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 should 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 foobar here
              The widget gateway ate it
      This will allow some useful information to be transferred.
      As the recipient is a human (IPMS), then suitable action
      should be available.
 3.   Finally both can be done.  In this case, the supplementary
      information in the (positive) Delivery Report should make

Kille [Page 64] RFC 1138 Mapping X.400(88) and 822 December 1989

      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], should be used to map the separate
 IPMS.BodyParts in the single RFC 822 message body.  If this is done,
 a "Message-Type:" field with value "Multiple part" should be added,
 which will indicate to a receiving gateway that the message may be
 unfolded according to RFC 934.
 For backwards compatibility with RFC 987, the following procedures
 should 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 should be appended to the RFC
 822 header.

5.3.5. Mappings from an IP Notification

 A message is generated, with the following fields:
 From:
      Set to the MTS.MessageDeliveryEnvelope.other-
      fields.originator-name.
 To:  Set to the IPMS.IPN.ipm-originator.
 Subject:
      Set to something of the form "X.400 Inter-Personal 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
 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>

Kille [Page 65] RFC 1138 Mapping X.400(88) and 822 December 1989

                  "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
         non-receipt-reason = "Discarded" / "Auto-Forwarded"
         discard-reason     = "Expired" / "Obsoleted" /
                                 "User Subscription Terminated"
         acknowledgement-mode = "Manually" / "Automatically"
 The mappings for elements of the common fields of IPMS.IPN
 (IPMS.CommonFields) onto this structure and the message header are:
      subject-ipm
           Mapped to "References:"

Kille [Page 66] RFC 1138 Mapping X.400(88) and 822 December 1989

      ipm-originator
           Mapped  to "To:".
      ipm-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
           If present, the second option of EBNF.ipn-content-return
           should be chosen, and an RFC 822 mapping of the message
           included.  Otherwise the first option should be chosen.
      The mappings for elements of IPMS.IPN.receipt-fields
      (IPMS.ReceiptFields) are:
      receipt-time
           Mapped to EBNF.receipt-time
      acknowledgement-mode
           Mapped to EBNF.acknowledgement-mode
      suppl-receipt-info
           Mapped to EBNF.ipn-suppl
 An example notification is:
    From: Steve Kille <steve@cs.ucl.ac.uk>
    To: Julian Onions <jpo@computer-science.nottingham.ac.uk>
    Subject: X400 Inter-personal Receipt Notification
    Message-Type: InterPersonal Notification
    References: <1229.614418325@UK.AC.NOTT.CS>
    Date: Wed, 21 Jun 89 08:45:25 +0100

Kille [Page 67] RFC 1138 Mapping X.400(88) and 822 December 1989

    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
    The Original Message is not available

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 ";"
              / "Redirection-History" ":" redirection
              / "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"
    redirection     = mailbox ";" "reason" "="
                            redirection-reason
                            ";" date-time

Kille [Page 68] RFC 1138 Mapping X.400(88) and 822 December 1989

    redirection-reason =
                    "Recipient Assigned Alternate Recipient"
                  / "Originator Requested Alternate Recipient"
                  / "Recipient MD Assigned Alternate Recipient"
    These elements are only appropriate for physical delivery.  They
    are represented as comments in the "X400-Recipients:" field, as
    described in Section 4.6.2.2.
 originator-certificate
 message-token
 content-confidentiality-algorithm-identifier
 content-integrity-check
 message-origin-authentication-check
 message-security-label
 proof-of-delivery-request
    These elements imply use of security services not available in the
    RFC 822 environment.  If they are marked as critical for transfer
    or delivery, then the message should be rejected.  Otherwise they
    should be discarded.
 redirection-history
      Each element is mapped to an extended RFC 822 field
      "Redirection-History:".  They should be ordered in the
      message header, so that the most recent redirection comes
      first (same order as trace).
 dl-expansion-history
      Each element is mapped to the extended RFC 822 field
      "DL-Expansion-History:".  They should 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 should be rejected.  If they are not so marked, they can
 safely be discarded.  The list of discarded fields should 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:

Kille [Page 69] RFC 1138 Mapping X.400(88) and 822 December 1989

  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 should be 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.  If this is due to differing service requests for
 each recipient, then a different message should be generated.
 If it is due only to the request for non-disclosure of
 recipients, then the "X400-Recipients:" field should be omitted,
 and only one message sent.
 The following EBNF is defined for extended RFC 822 headers:
    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-and-mta ";"  ]
                        action-list
                        ";" arrival-time
    md-and-mta       = [ "mta" mta "in" ]  global-id
    mta              = word
    arrival-time     = date-time
    action-list      = 1#action
    action           = "Redirected"
                     / "Expanded"
                     / "Relayed"
                     / "Rerouted"
 If MTA.PerMessageTransferFields.deferred-delivery-time is present,
 use it to generate a Deferred-Delivery: field.  For some reason,
 X.400 does not make this information available at the MTS level on

Kille [Page 70] RFC 1138 Mapping X.400(88) and 822 December 1989

 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 should
 hold the message until the time specified in the protocol element.
 Thus, it is expected that the value of this element will often 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.
 Use this to generate a sequence of "X400-Received:" fields.  The only
 difference between external trace and internal trace will be the
 extra MTA information in internal trace elements.
 When generating an RFC 822 message all trace fields (X400- Received
 and Received) should be at the beginning of the header, before any
 other fields.  Trace should be in chronological order, with the most
 recent element at the front of the message.  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 should be generated with the following fields:

Kille [Page 71] RFC 1138 Mapping X.400(88) and 822 December 1989

 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:
      Something of the form "X.400 Delivery Report".
 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.
 This gives a summary of critical information, and then a full listing
 of all parameters:
 dr-body-format = dr-summary <CRLF>
                  dr-recipients <CRLF>
                  dr-extra-information <CRLF>
                  dr-content-return
 dr-content-return = "The Original Message is not available"
                 / "The Original Message follows:"
                   <CRLF> <CRLF> message
 dr-summary = "This report relates to your message:" <CRLF>
              content-correlator <CRLF> <CRLF>
              "of" date-time <CRLF> <CRLF>
              "It was generated by:" report-point <CRLF>
              "at" date-time <CRLF> <CRLF>
              "It was later converted to RFC 822 by:" mailbox <CRLF>
              "at" 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

Kille [Page 72] RFC 1138 Mapping X.400(88) and 822 December 1989

 dr-recip-failure = "Your message was not delivered to:"
                 mailbox <CRLF>
                 "for the following reason:" *word
 dr-extra-information =
  "-----------------------------------------------" <CRLF> <CRLF>
  "The following information is derived from the Report" <CRLF>
  "It may be useful for problem diagnosis:" <CRLF> <CRLF>
  drc-field-list
 drc-field-list       = *(drc-field <CRLF>)
 drc-field = "Subject-Submission-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 ";" ]

Kille [Page 73] RFC 1138 Mapping X.400(88) and 822 December 1989

 report-point = [ "mta" word "in" ] global-id
 content-correlator = *word
 dl-history = 1#( mailbox "(" date-time ")")
 The format is defined as a fixed definition.  The only exception is
 that the EBNF.drc-fields should follow 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)
 content-type
      Mapped to EBNF.drc-field (Content-Type)
 original-encoded-information-types
      Mapped to EBNF.drc-field (Encoded-Info)
 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 should 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 should not be present.  If they are,
    they should be discarded in preference to discarding the whole
    report.

Kille [Page 74] RFC 1138 Mapping X.400(88) and 822 December 1989

 For each element of MTS.ReportDeliveryEnvelope.per-recipient-fields,
 a value of EBNF.dr-recipient, and an EBNF.drc-field (Recipient-Info)
 should be 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
      should be filled in systematically.
 converted-encoded-information-types
      Set EBNF.drc-field ("converted eits")
 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 should be discarded, irrespective of
 criticality.

Kille [Page 75] RFC 1138 Mapping X.400(88) and 822 December 1989

 The original message should be included in the delivery port.  The
 original message will usually be available at the gateway, as
 discussed in Section 5.2.

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 should be made:
 MTA.ReportTransferEnvelope.report-destination-name
      This should be used to generate the To: field.
 MTA.ReportTransferEnvelope.identifier
      Mapped to the extended RFC 822 field "X400-MTS-Identifier:".
      It may also be used to derive a "Message-Id:" field.
 MTA.ReportTransferEnvelope.trace-information
      and
 MTA.ReportTransferEnvelope.internal-trace-information
      Mapped onto the extended RFC 822 field "X400-Received:", as
      described in Section 5.3.7.  The first element should also
      be used to generate the "Date:" field, and the
      EBNF.failure-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 should be ordered so that the most recent trace element
    comes first.

5.3.8.3. Example Delivery Report

 This is an example, of a moderately complex report.
 From: The Postmaster <postmaster@cs.ucl.ac.uk>
 To: jpo@computer-science.nottingham.ac.uk
 Subject: X.400 Delivery Report
 Message-Type: Delivery Report
 Date: Wed, 21 Jun 89 08:45:25 +0100
 X400-MTS-Identifier: /PRMD=UK.AC/ADMD=Gold 400/C=GB/;13412345235

Kille [Page 76] RFC 1138 Mapping X.400(88) and 822 December 1989

 This report relates to your message:
   Date: Wed, 21 Jun 89 06:15:43 +0000
   Message-ID:  <8907140715.aa09015@CS.Nott.AC.UK>
   Subject: Now it's the fine tuning .... !
   To: Piete Brooks (Postmaster) <pb@computer-lab.cambridge.ac.uk>
 of Wed, 21 Jun 89 06:15:43 +0000
 It was generated by mta PK in /PRMD=UK/ADMD=DBP/C=DE/
 at Wed, 21 Jun 89 08:45:25 +0100
 It was later converted to RFC 822 by: Mail-Gateway@oxbridge.ac.uk
 at Wed, 21 Jun 89 08:45:26 +0100
 Your message was not delivered to: bad-user@nowhere
 for the following reason: Rendition problem with punctuation
         (Umlaut failure)
  1. ———————————————-
 The following information is derived from the Report
 It may be useful for problem diagnosis:
 Subject-Submission-Identifier:
                        [/PRMD=UK.AC/ADMD=Gold 400/C=GB/;148996]
 Content-Identifier:  X.400 Delivery Report
 Content-Type: P2-1988 (22)
 Original-Encoded-Information-Types: ia5
 Content-Correlator: Date: Wed, 21 Jun 89 06:15:43 +0000
     Message-ID:  <8907140715.aa09015@CS.Nott.AC.UK>
     Subject: Now it's the fine tuning .... !
     To: Piete Brooks (Postmaster) <pb@computer-lab.cambridge.ac.uk>
 Recipient-Info:
     bad-user@nowhere, /S=bad-user/PRMD=nowhere/ADMD=DBP/C=DE/ ;
     FAILURE reason Physical-Rendition-Not-Performed (3) ;
     diagnostic Punctuation-Symbol-Loss (23) ;
     supplementary info Umlaut failure
 The Original Message follows:
 Subject: Now it's the fine tuning .... !
 Date: Wed, 21 Jun 89 06:15:43 +0000
 From: Julian Onions <jpo@computer-science.nottingham.ac.uk>
 To: Piete Brooks (Postmaster) <pb@computer-lab.cambridge.ac.uk>
 Cc: bad-user@nowhere
 Message-ID:  <8907140715.aa09015@CS.Nott.AC.UK>
 A short test

Kille [Page 77] RFC 1138 Mapping X.400(88) and 822 December 1989

5.3.9. Probe

 This is an MTS internal issue.  Any probe should 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 should
 make use of MTS.SupplementaryInformation to indicate that the probe
 was serviced by the gateway.

Appendix A - Differences with RFC 987

 This appendix summarises changes between this document and RFC
 987/RFC 1026.

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.

Kille [Page 78] RFC 1138 Mapping X.400(88) and 822 December 1989

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 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
 must be used.

3. 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.

Kille [Page 79] RFC 1138 Mapping X.400(88) and 822 December 1989

 If an Acknowledge-To: field is present when going from JNT Mail to
 X.400, MTS.PerRecipientSubmissionFields.originator-request-
 report.report shall be set for each recipient.  If there is more that
 one address in the Acknowledge-To: field, or if the one address is
 not equivalent to the 822-MTS return address, then:
    1.   Acknowledgement(s) should be generated by the gateway.  The
         text of these acknowledgements should indicate that they are
         generated by the gateway.
    2.   The Acknowledge-To: field should also be passed as an
         extension heading.
 When going from X.400 to JNT Mail, in cases where
 MTA.PerRecipientMessageTransferFields.per-recipient-indicators.
 originator-report is set, the copy of the message to that recipient
 should have an Acknowledge-To: field containing the
 MTS.OtherMessageDeliveryFields.originator-name.  No special treatment
 should be given when MTA.PerRecipientMessageTransferFields.per-
 recipient-indicators.  originating-MTA-report is set.  No attempt
 should be made to map Receipt notification requests onto
 Acknowledge-To:, as no association can be guaranteed between IPMS and
 MTS level addressing information.

4. 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 should be used.
 The trace text, including the "Via:", should be 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.

5. Timezone specification

 The extended syntax of zone defined in the JNT Mail Protocol should
 be used in the mapping of UTCTime defined in Chapter 3.

6. 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: field.
 To overcome this, new extended JNT Mail field is defined.  This is
 chosen to align with the JNT recommendation for interworking with

Kille [Page 80] RFC 1138 Mapping X.400(88) and 822 December 1989

 full RFC 822 systems [Kille84b].
    original-sender     = "Original-Sender" ":" mailbox
 If an IPM has no IPMS.Heading.authorising-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.authorising-users component, and
 IPMS.Heading.originator.formal-name is different from
 MTS.OtherMessageDeliveryFields.originator-name,
 MTS.OtherMessageDeliveryFields.originator-name should be 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-Internet gateway and gatehost.COM is an
 Internet-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:
    Country         US
    ADMD            ATT

Kille [Page 81] RFC 1138 Mapping X.400(88) and 822 December 1989

    PRMD            Internet
    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 should be used.
    rfc-987-88 OBJECT IDENTIFIER ::=
        {ccitt data(9) pss(2342) ucl(234219200300) rfc-987-88(200)}
    id-rfc-822-field OBJECT IDENTIFIER ::= {rfc987-88 field(0)}

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 ")"

Kille [Page 82] RFC 1138 Mapping X.400(88) and 822 December 1989

 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, 1-9, and "-">
 object-identifier ::= [ defined-value ] oid-comp-list
 oid-comp-list ::= oid-comp oid-comp-list
                 | oid-comp
 defined-value ::= key-string
 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

Kille [Page 83] RFC 1138 Mapping X.400(88) and 822 December 1989

 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        = "$" ps-char
 dmn-or-address  = dmn-part *( "." dmn-part )
 dmn-part        = attribute "$" 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-and-mta ";"  ]
                     action-list
                     ";" arrival-time

Kille [Page 84] RFC 1138 Mapping X.400(88) and 822 December 1989

 md-and-mta       = [ "mta" mta "in" ]  global-id
 mta              = word
 arrival-time     = date-time
 action-list      = 1#action
 action           = "Redirected"
                  / "Expanded"
                  / "Relayed"
                  / "Rerouted"
 dr-body-format = dr-summary <CRLF>
                  dr-recipients <CRLF>
                  dr-extra-information <CRLF>
                  dr-content-return
 dr-content-return = "The Original Message is not available"
                 / "The Original Message follows:"
                   <CRLF> <CRLF> message
 dr-summary = "This report relates to your message:" <CRLF>
                 content-correlator <CRLF> <CRLF>
              "of" date-time <CRLF> <CRLF>
              "It was generated by:" report-point <CRLF>
              "at" date-time <CRLF> <CRLF>
              "It was later converted to RFC 822 by:" mailbox <CRLF>
              "at" 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-extra-information =
  "-----------------------------------------------" <CRLF> <CRLF>
  "The following information is derived from the Report" <CRLF>

Kille [Page 85] RFC 1138 Mapping X.400(88) and 822 December 1989

  "It may be useful for problem diagnosis:" <CRLF> <CRLF>
 drc-field-list
 drc-field-list       = *(drc-field <CRLF>)
 drc-field = "Subject-Submission-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
 recipient-info  = mailbox "," std-or ";"
                 report-type
                 [ "converted eits" encoded-info ";" ]
                 [ "originally intended recipient"
                         mailbox "," std-or ";" ]
                 [ "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 ")")
 mts-field = "X400-MTS-Identifier" ":" mts-msg-id
           / "X400-Originator" ":" mailbox
           / "X400-Recipients" ":" 1#mailbox
           / "Original-Encoded-Information-Types" ":"

Kille [Page 86] RFC 1138 Mapping X.400(88) and 822 December 1989

                             encoded-info
           / "X400-Content-Type" ":" mts-content-type
           / "Content-Identifier" ":" printablestring
           / "Priority" ":" priority
           / "Originator-Return-Address" ":" 1#mailbox
           / "DL-Expansion-History" ":" mailbox ";" date-time ";"
           / "Redirection-History" ":" redirection
           / "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"
 redirection     = mailbox ";" "reason" "="
                         redirection-reason
                         ";" date-time
 redirection-reason =
           "Recipient Assigned Alternate Recipient"
         / "Originator Requested Alternate Recipient"
         / "Recipient MD Assigned Alternate Recipient"
 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:"

Kille [Page 87] RFC 1138 Mapping X.400(88) and 822 December 1989

          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
 non-receipt-reason = "Discarded" / "Auto-Forwarded"
 discard-reason     = "Expired" / "Obsoleted" /
                         "User Subscription Terminated"
 acknowledgement-mode = "Manually" / "Automatically"
 ms-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

Kille [Page 88] RFC 1138 Mapping X.400(88) and 822 December 1989

 importance      = "low" / "normal" / "high"
 sensitivity     = "Personal" / "Private" /
                        "Company-Confidential"
 language        = 2*ALPHA [ language-description ]
 language-description = printable-string
 message-type    = "Delivery Report"
                 / "InterPersonal Notification"
                 / "Multiple Part"

Appendix F - Format of address mapping tables

 There is a need to specify the association between the domain and
 X.400 namespaces described in Chapter 4.  The use of this association
 leads to a better service on both sides of the gateway, and so
 defining mappings and distributing them in the form defined in this
 appendix is strongly encouraged.
 This syntax defined is initially in table form, but the syntax is
 defined in a manner which makes it suitable for use with domain
 nameservices (such as the Internet Domain nameservers or the UK NRS).
 The mapping is not symmetric, and so a separate table is specified
 for each direction.  If multiple matches are possible, the longest
 possible match should be used.
 First, an address syntax is defined, which is compatible with the
 syntax used for 822.domains.  It is intended that this syntax may be
 used in conjunction with systems which support this form of name.
 To allow the mapping of null attributes  to be represented, the
 pseudo-value "@" (not a printable string character) is used to
 indicate omission of a level in the hierarchy.  This is distinct from
 the form including the element with no value, although a correct
 X.400 implementation will interpret both in the same manner.
 This syntax is not intended to be handled by users.
    dmn-or-address  = dmn-part *( "." dmn-part )
    dmn-part        = attribute "$" value
    attribute       = standard-type
                    / "~" dmn-printablestring
    value           = dmn-printablestring
                    / "@"

Kille [Page 89] RFC 1138 Mapping X.400(88) and 822 December 1989

    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.
 Various further restrictions are placed on the usage of dmn-or-
 address:
 1.   Only C, ADMD, PRMD, O, and OU may be used.
 2.   There must be a strict ordering of all components, with the
      most significant components on the RHS.
 3.   No components may be omitted from the hierarchy, although
      the hierarchy may terminate at any level.  If the mapping is
      to an omitted component, the "@" syntax is used.
 For domain -> X.400:
        domain-syntax "#" dmn-or-address "#"
 Note that the trailing "#" is used for clarity, as the dmn-or-
 address syntax can 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#
 For X.400 -> domain:
    dmn-or-address "#" domain-syntax "#"
    For example:
    #
    # Mapping table

Kille [Page 90] RFC 1138 Mapping X.400(88) and 822 December 1989

    #
    PRMD$UK.AC.ADMD$GOLD 400.C$GB#AC.UK#

References

 [Braden89a]  Braden, R., Editor, "Requirements for Internet Hosts --
 Application and Support", RFC 1123, USC/Information Sciences
 Institute, October 1989.
 [CCITT88a]  CCITT, "CCITT Recommendations X.408", Message Handling
 Systems: Encoded Information Type Conversion Rules, CCITT, December
 1988.
 [CCITT/ISO88a]  CCITT/ISO, "CCITT Recommendations X.400/ ISO IS
 10021-1", Message Handling: System and Service Overview, CCITT/ISO,
 December 1988.
 [CCITT/ISO88b]  CCITT/ISO, "CCITT Recommendations X.420/ ISO IS
 10021-7", Message Handling Systems: Interpersonal Messaging System,
 CCITT/ISO, 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, CCITT/ISO, December 1988.
 [CCITT/ISO88d]  CCITT/ISO, "Specification of Abstract Syntax Notation
 One (ASN.1)", CCITT Recommendation X.208 / ISO IS 8824, CCITT/ISO,
 December 1988.
 [Crocker82a]  Crocker, D., "Standard of the Format of ARPA Internet
 Text Messages", RFC 822, August 1982.
 [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",

Kille [Page 91] RFC 1138 Mapping X.400(88) and 822 December 1989

 UCL Research Note 89/14, March 1989.
 [Kille89b]  Kille, S., "Mapping Between Full RFC 822 and RFC 822 with
 Restricted Encoding", RFC 1137, December 1989.
 [Larmouth83a]  Larmouth, J., "JNT Name Registration Technical Guide",
 Salford University Computer Centre, April 1983.
 [Mockapetris87a]  Mockapetris, P., "Domain Names - Concepts and
 Facilities", RFC 1034, USC/Information Sciences Institute, November
 1987.
 [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.
 [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 Kille
 University College London
 Gower Street
 WC1E 6BT
 England
 Phone: +44-1-380-7294
 EMail: S.Kille@Cs.Ucl.AC.UK

Kille [Page 92]

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