RFC 1327
Mapping between X.400(1988) / ISO 10021 and RFC 822
Pages: 113
Obsoletes: 0987 1026 1138 1148
Obsoleted by: 2156
Updates: 0822
Updated by: 1495
Obsoletes: 0987 1026 1138 1148
Obsoleted by: 2156
Updates: 0822
Updated by: 1495
Part 1 of 4 – Pages 1 to 24
Network Working Group S. Hardcastle-Kille Request for Comments: 1327 University College London Obsoletes: RFCs 987, 1026, 1138, 1148 May 1992 Updates: RFC 822 Mapping between X.400(1988) / ISO 10021 and RFC 822 Status of this Memo This RFC specifies an IAB standards track protocol for the Internet community, and requests discussion and suggestions for improvements. Please refer to the current edition of the "IAB Official Protocol Standards" for the standardization state and status of this protocol. Distribution of this memo is unlimited. Abstract This document describes a set of mappings which will enable interworking between systems operating the CCITT X.400 1988) Recommendations on Message Handling Systems / ISO IEC 10021 Message Oriented Text Interchange Systems (MOTIS) [CCITT/ISO88a], and systems using the RFC 822 mail protocol [Crocker82a] or protocols derived from RFC 822. The approach aims to maximise the services offered across the boundary, whilst not requiring unduly complex mappings. The mappings should not require any changes to end systems. This document is a revision based on RFCs 987, 1026, 1138, and 1148 [Kille86a,Kille87a] which it obsoletes. This document specifies a mapping between two protocols. This specification should be used when this mapping is performed on the DARPA Internet or in the UK Academic Community. This specification may be modified in the light of implementation experience, but no substantial changes are expected. Table of Contents 1 - Overview ...................................... 3 1.1 - X.400 ......................................... 3 1.2 - RFC 822 ....................................... 3 1.3 - The need for conversion ....................... 4 1.4 - General approach .............................. 4 1.5 - Gatewaying Model .............................. 5 1.6 - X.400 (1984) .................................. 8 1.7 - Compatibility with previous versions .......... 8 1.8 - Aspects not covered ........................... 8 1.9 - Subsetting .................................... 9 1.10 - Document Structure ............................ 9
1.11 - Acknowledgements .............................. 9 2 - Service Elements .............................. 10 2.1 - The Notion of Service Across a Gateway ........ 10 2.2 - RFC 822 ....................................... 11 2.3 - X.400 ......................................... 15 3 - Basic Mappings ................................ 24 3.1 - Notation ...................................... 24 3.2 - ASCII and IA5 ................................. 26 3.3 - Standard Types ................................ 26 3.4 - Encoding ASCII in Printable String ............ 28 4 - Addressing .................................... 30 4.1 - A textual representation of MTS.ORAddress ..... 30 4.2 - Basic Representation .......................... 31 4.3 - EBNF.822-address <-> MTS.ORAddress ............ 36 4.4 - Repeated Mappings ............................. 48 4.5 - Directory Names ............................... 50 4.6 - MTS Mappings .................................. 50 4.7 - IPMS Mappings ................................. 55 5 - Detailed Mappings ............................. 59 5.1 - RFC 822 -> X.400 .............................. 59 5.2 - Return of Contents ............................ 67 5.3 - X.400 -> RFC 822 .............................. 67 Appendix A - Mappings Specific to SMTP ..................... 91 Appendix B - Mappings specific to the JNT Mail ............. 91 1 - Introduction .................................. 91 2 - Domain Ordering ............................... 91 3 - Addressing .................................... 91 4 - Acknowledge-To: .............................. 91 5 - Trace ......................................... 92 6 - Timezone specification ........................ 92 7 - Lack of 822-MTS originator specification ...... 92 Appendix C - Mappings specific to UUCP Mail ................ 93 Appendix D - Object Identifier Assignment .................. 94 Appendix E - BNF Summary ................................... 94 Appendix F - Format of address mapping tables .............. 101 1 - Global Mapping Information .................... 101 2 - Syntax Definitions ............................ 102 3 - Table Lookups ................................. 103 4 - Domain -> O/R Address format .................. 104 5 - O/R Address -> Domain format .................. 104 6 - Domain -> O/R Address of Gateway table ........ 104 Appendix G - Mapping with X.400(1984) ...................... 105 Appendix H - RFC 822 Extensions for X.400 access ........... 106 Appendix I - Conformance ................................... 106 Appendix J - Change History: RFC 987, 1026, 1138, 1148 ..... 107 1 - Introduction .................................. 108 2 - Service Elements .............................. 108 3 - Basic Mappings ................................ 108
4 - Addressing .................................... 108 5 - Detailed Mappings ............................. 109 6 - Appendices .................................... 109 Appendix K - Change History: RFC 1148 to this Document ..... 109 1 - General ....................................... 109 2 - Basic Mappings ................................ 110 3 - Addressing .................................... 110 4 - Detailed Mappings ............................. 110 5 - Appendices .................................... 110 References ................................................. 111 Security Considerations .................................... 113 Author's Address ........................................... 113 Chapter 1 -- Overview 1.1. X.400 This document relates to the CCITT 1988 X.400 Series Recommendations / ISO IEC 10021 on the Message Oriented Text Interchange Service (MOTIS). This ISO/CCITT standard is referred to in this document as "X.400", which is a convenient shorthand. Any reference to the 1984 CCITT Recommendations will be explicit. X.400 defines an Interpersonal Messaging System (IPMS), making use of a store and forward Message Transfer System. This document relates to the IPMS, and not to wider application of X.400. It is expected that X.400 will be implemented very widely. 1.2. RFC 822 RFC 822 evolved as a messaging standard on the DARPA (the US Defense Advanced Research Projects Agency) Internet. It specifies and end to end message format. It is used in conjunction with a number of different message transfer protocol environments. SMTP Networks On the DARPA Internet and other TCP/IP networks, RFC 822 is used in conjunction with two other standards: RFC 821, also known as Simple Mail Transfer Protocol (SMTP) [Postel82a], and RFC 920 which is a Specification for domains and a distributed name service [Postel84a]. UUCP Networks UUCP is the UNIX to UNIX CoPy protocol, which is usually used over dialup telephone networks to provide a simple message transfer mechanism. There are some extensions to RFC 822, particularly in the addressing. They use domains which conform to RFC 920, but not the corresponding domain nameservers [Horton86a].
Bitnet
Some parts of Bitnet and related networks use RFC 822
related protocols, with EBCDIC encoding.
JNT Mail Networks
A number of X.25 networks, particularly those associated
with the UK Academic Community, use the JNT (Joint Network
Team) Mail Protocol, also known as Greybook [Kille84a].
This is used with domains and name service specified by the
JNT NRS (Name Registration Scheme) [Larmouth83a].
The mappings specified here are appropriate for all of these
networks.
1.3. The need for conversion
There is a large community using RFC 822 based protocols for mail
services, who will wish to communicate with users of the IPMS
provided by X.400 systems. This will also be a requirement in cases
where communities intend to make a transition to use of an X.400
IPMS, as conversion will be needed to ensure a smooth service
transition. It is expected that there will be more than one gateway,
and this specification will enable them to behave in a consistent
manner. Note that the term gateway is used to describe a component
performing the protocol mappings between RFC 822 and X.400. This is
standard usage amongst mail implementors, but should be noted
carefully by transport and network service implementors.
Consistency between gateways is desirable to provide:
1. Consistent service to users.
2. The best service in cases where a message passes through
multiple gateways.
1.4. General approach
There are a number of basic principles underlying the details of the
specification. These principles are goals, and are not achieved in
all aspects of the specification.
1. The specification should be pragmatic. There should not be
a requirement for complex mappings for "Academic" reasons.
Complex mappings should not be required to support trivial
additional functionality.
2. Subject to 1), functionality across a gateway should be as
high as possible.
3. It is always a bad idea to lose information as a result of
any transformation. Hence, it is a bad idea for a gateway
to discard information in the objects it processes. This
includes requested services which cannot be fully mapped.
4. All mail gateways actually operate at exactly one level
above the layer on which they conceptually operate. This
implies that the gateway must not only be cognisant of the
semantics of objects at the gateway level, but also be
cognisant of higher level semantics. If meaningful
transformation of the objects that the gateway operates on
is to occur, then the gateway needs to understand more than
the objects themselves.
5. Subject to 1), the specification should be reversible. That
is, a double transformation should bring you back to where
you started.
1.5. Gatewaying Model
1.5.1. X.400
X.400 defines the IPMS Abstract Service in X.420/ISO 10021-7,
[CCITT/ISO88b] which comprises of three basic services:
1. Origination
2. Reception
3. Management
Management is a local interaction between the user and the IPMS, and
is therefore not relevant to gatewaying. The first two services
consist of operations to originate and receive the following two
objects:
1. IPM (Interpersonal Message). This has two components: a
heading, and a body. The body is structured as a sequence
of body parts, which may be basic components (e.g., IA5
text, or G3 fax), or IP Messages. The heading consists of
fields containing end to end user information, such as
subject, primary recipients (To:), and importance.
2. IPN (Inter Personal Notification). A notification about
receipt of a given IPM at the UA level.
The Origination service also allows for origination of a probe, which
is an object to test whether a given IPM could be correctly received.
The Reception service also allows for receipt of Delivery Reports DR), which indicate delivery success or failure. These IPMS Services utilise the Message Transfer (MT) Abstract Service [CCITT/ISO88c]. The MT Abstract Service provides the following three basic services: 1. Submission (used by IPMS Origination) 2. Delivery (used by IPMS Reception) 3. Administration (used by IPMS Management) Administration is a local issue, and so does not affect this standard. Submission and delivery relate primarily to the MTS Message (comprising Envelope and Content), which carries an IPM or IPN (or other uninterpreted contents). There is also an Envelope, which includes an ID, an originator, and a list of recipients. Submission also includes the probe service, which supports the IPMS Probe. Delivery also includes Reports, which indicate whether a given MTS Message has been delivered or not. The MTS is REFINED into the MTA (Message Transfer Agent) Service, which defines the interaction between MTAs, along with the procedures for distributed operation. This service provides for transfer of MTS Messages, Probes, and Reports. 1.5.2. RFC 822 RFC 822 is based on the assumption that there is an underlying service, which is here called the 822-MTS service. The 822-MTS service provides three basic functions: 1. Identification of a list of recipients. 2. Identification of an error return address. 3. Transfer of an RFC 822 message. It is possible to achieve 2) within the RFC 822 header. Some 822-MTS protocols, in particular SMTP, can provide additional functionality, but as these are neither mandatory in SMTP, nor available in other 822-MTS protocols, they are not considered here. Details of aspects specific to two 822-MTS protocols are given in Appendices B and C. An RFC 822 message consists of a header, and content which is uninterpreted ASCII text. The header is divided into fields, which are the protocol elements. Most of these fields are analogous to P2 heading fields, although some are analogous to MTS Service Elements
or MTA Service Elements. 1.5.3. The Gateway Given this functional description of the two services, the functional nature of a gateway can now be considered. It would be elegant to consider the 822-MTS service mapping onto the MTS Service Elements and RFC 822 mapping onto an IPM, but reality just does not fit. Another elegant approach would be to treat this document as the definition of an X.400 Access Unit (AU). Again, reality does not fit. It is necessary to consider that the IPM format definition, the IPMS Service Elements, the MTS Service Elements, and MTA Service Elements on one side are mapped into RFC 822 + 822-MTS on the other in a slightly tangled manner. The details of the tangle will be made clear in Chapter 5. Access to the MTA Service Elements is minimised. The following basic mappings are thus defined. When going from RFC 822 to X.400, an RFC 822 message and the associated 822-MTS information is always mapped into an IPM (MTA, MTS, and IPMS Services). Going from X.400 to RFC 822, an RFC 822 message and the associated 822-MTS information may be derived from: 1. A Report (MTA, and MTS Services) 2. An IPN (MTA, MTS, and IPMS services) 3. An IPM (MTA, MTS, and IPMS services) Probes (MTA Service) must be processed by the gateway, as discussed in Chapter 5. MTS Messages containing Content Types other than those defined by the IPMS are not mapped by the gateway, and should be rejected at the gateway. 1.5.4. Repeated Mappings The primary goal of this specification is to support single mappings, so that X.400 and RFC 822 users can communicate with maximum functionality. The mappings specified here are designed to work where a message traverses multiple times between X.400 and RFC 822. This is often essential, particularly in the case of distribution lists. However, in general, this will lead to a level of service which is the lowest common denominator (approximately the services offered by RFC 822). Some RFC 822 networks may wish to use X.400 as an interconnection mechanism (typically for policy reasons), and this is fully supported.
Where an X.400 messages transfers to RFC 822 and then back to X.400, there is no expectation of X.400 services which do not have an equivalent service in standard RFC 822 being preserved - although this may be possible in some cases. 1.6. X.400 (1984) Much of this work is based on the initial specification of RFC 987 and in its addendum RFC 1026, which defined a mapping between X.400(1984) and RFC 822. A basic decision is that the mapping defined in this document is to the full 1988 version of X.400, and not to a 1984 compatible subset. New features of X.400(1988) can be used to provide a much cleaner mapping than that defined in RFC 987. This is important, to give good support to communities which will utilise full X.400 at an early date. To interwork with 1984 systems, Appendix G shall be followed. If a message is being transferred to an X.400(1984) system by way of X.400(1988) MTA it will give a slightly better service to follow the rules of Appendix G. 1.7. Compatibility with previous versions The changes between this and older versions of the document are given in Appendices I and J. These are RFCs 987, 1026, 1138, and 1148. This document is a revision of RFC 1148 [Kille90a]. As far as possible, changes have been made in a compatible fashion. 1.8. Aspects not covered There have been a number of cases where RFC 987 was used in a manner which was not intended. This section is to make clear some limitations of scope. In particular, this specification does not specify: - Extensions of RFC 822 to provide access to all X.400 services - X.400 user interface definition - Mapping X.400 to extended versions of RFC 822, with support for multimedia content. The first two of these are really coupled. To map the X.400 services, this specification defines a number of extensions to RFC 822. As a side effect, these give the 822 user access to SOME X.400 services. However, the aim on the RFC 822 side is to preserve current service, and it is intentional that access is not given to
all X.400 services. Thus, it will be a poor choice for X.400 implementors to use RFC 987(88) as an interface - there are too many aspects of X.400 which cannot be accessed through it. If a text interface is desired, a specification targeted at X.400, without RFC 822 restrictions, would be more appropriate. Some optional and limited extensions in this area have proved useful, and are defined in Appendix H. 1.9. Subsetting This proposal specifies a mapping which is appropriate to preserve services in existing RFC 822 communities. Implementations and specifications which subset this specification are strongly discouraged. 1.10. Document Structure This document has five chapters: 1. Overview - this chapter. 2. Service Elements - This describes the (end user) services mapped by a gateway. 3. Basic mappings - This describes some basic notation used in Chapters 3-5, the mappings between character sets, and some fundamental protocol elements. 4. Addressing - This considers the mapping between X.400 O/R names and RFC 822 addresses, which is a fundamental gateway component. 5. Detailed Mappings - This describes the details of all other mappings. There are also eleven appendices. WARNING: THE REMAINDER OF THIS SPECIFICATION IS TECHNICALLY DETAILED. IT WILL NOT MAKE SENSE, EXCEPT IN THE CONTEXT OF RFC 822 AND X.400 (1988). DO NOT ATTEMPT TO READ THIS DOCUMENT UNLESS YOU ARE FAMILIAR WITH THESE SPECIFICATIONS. 1.11. Acknowledgements The work in this specification was substantially based on RFC 987 and RFC 1148, which had input from many people, who are credited in the respective documents.
A number of comments from people on RFC 1148 lead to this document. In particular, there were comments and suggestions from: Maurice Abraham (HP); Harald Alvestrand (Sintef); Peter Cowen (X-Tel); Jim Craigie (JNT); Ella Gardener (MITRE); Christian Huitema (Inria); Erik Huizer (SURFnet); Neil Jones DEC); Ignacio Martinez (IRIS); Julian Onions (X-Tel); Simon Poole (SWITCH); Clive Roberts (Data General); Pete Vanderbilt SUN); Alan Young (Concurrent). Chapter 2 - Service Elements This chapter considers the services offered across a gateway built according to this specification. It gives a view of the functionality provided by such a gateway for communication with users in the opposite domain. This chapter considers service mappings in the context of SINGLE transfers only, and not repeated mappings through multiple gateways. 2.1. The Notion of Service Across a Gateway RFC 822 and X.400 provide a number of services to the end user. This chapter describes the extent to which each service can be supported across an X.400 <-> RFC 822 gateway. The cases considered are single transfers across such a gateway, although the problems of multiple crossings are noted where appropriate. 2.1.1. Origination of Messages When a user originates a message, a number of services are available. Some of these imply actions (e.g., delivery to a recipient), and some are insertion of known data (e.g., specification of a subject field). This chapter describes, for each offered service, to what extent it is supported for a recipient accessed through a gateway. There are three levels of support: Supported The corresponding protocol elements map well, and so the service can be fully provided. Not Supported The service cannot be provided, as there is a complete mismatch. Partial Support The service can be partially fulfilled. In the first two cases, the service is simply marked as Supported" or "Not Supported". Some explanation may be given if there are additional implications, or the (non) support is not intuitive. For
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: - Semantic correspondence. - No (significant) loss of information. - Any actions required by the service element. An example of a service gaining full support: If an RFC 822 originator specifies a Subject: field, this is considered to be supported, as an X.400 recipient will get a subject indication. In many cases, the required action will simply be to make the information available to the end user. In other cases, actions may imply generating a delivery report. All RFC 822 services are supported or partially supported for origination. The implications of non-supported X.400 services is described under X.400. 2.1.2. Reception of Messages For reception, the list of service elements required to support this mapping is specified. This is really an indication of what a recipient might expect to see in a message which has been remotely originated. 2.2. RFC 822 RFC 822 does not explicitly define service elements, as distinct from protocol elements. However, all of the RFC 822 header fields, with the exception of trace, can be regarded as corresponding to implicit RFC 822 service elements. 2.2.1. Origination in RFC 822 A mechanism of mapping, used in several cases, is to map the RFC 822 header into a heading extension in the IPM (InterPersonal Message).
This can be regarded as partial support, as it makes the information available to any X.400 implementations which are interested in these services. Communities which require significant RFC 822 interworking are recommended to require that their X.400 User Agents are able to display these heading extensions. Support for the various service elements (headers) is now listed. Date: Supported. From: Supported. For messages where there is also a sender field, the mapping is to "Authorising Users Indication", which has subtly different semantics to the general RFC 822 usage of From:. Sender: Supported. Reply-To: Supported. To: Supported. Cc: Supported. Bcc: Supported. Message-Id: Supported. In-Reply-To: Supported, for a single reference. Where multiple references are given, partial support is given by mapping to "Cross Referencing Indication". This gives similar semantics. References: Supported. Keywords: Supported by use of a heading extension. 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:
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: Reply-By: Requested-Delivery-Method: Sensitivity: X400-Content-Type: X400-MTS-Identifier:
X400-Originator: X400-Received: X400-Recipients: 2.3. X.400 2.3.1. Origination in X.400 When mapping services from X.400 to RFC 822 which are not supported by RFC 822, new RFC 822 headers are defined. It is intended that these fields will be registered, and that co- operating RFC 822 systems may use them. Where these new fields are used, and no system action is implied, the service can be regarded as being partially supported. Chapter 5 describes how to map X.400 services onto these new headers. Other elements are provided, in part, by the gateway as they cannot be provided by RFC 822. Some service elements are marked N/A (not applicable). There are five cases, which are marked with different comments: N/A (local) These elements are only applicable to User Agent / Message Transfer Agent interaction and so they cannot apply to RFC 822 recipients. N/A (PDAU) These service elements are only applicable where the recipient is reached by use of a Physical Delivery Access Unit (PDAU), and so do not need to be mapped by the gateway. N/A (reception) These services are only applicable for reception. N/A (prior) If requested, this service must be performed prior to the gateway. N/A (MS) These services are only applicable to Message Store (i.e., a local service). Finally, some service elements are not supported. In particular, the new security services are not mapped onto RFC 822. Unless otherwise indicated, the behaviour of service elements marked as not supported will depend on the criticality marking supplied by the user. If the element is marked as critical for transfer or delivery, a non-
delivery notification will be generated. Otherwise, the service request will be ignored. 2.3.1.1. Basic Interpersonal Messaging Service These are the mandatory IPM services as listed in Section 19.8 of X.400 / ISO/IEC 10021-1, listed here in the order given. Section 19.8 has cross references to short definitions of each service. Access management N/A (local). Content Type Indication Supported by a new RFC 822 header (Content-Type:). Converted Indication Supported by a new RFC 822 header (X400-Received:). Delivery Time Stamp Indication N/A (reception). IP Message Identification Supported. Message Identification Supported, by use of a new RFC 822 header (X400-MTS-Identifier). This new header is required, as X.400 has two message-ids whereas RFC 822 has only one (see previous service). Non-delivery Notification Not supported, although in general an RFC 822 system will return error reports by use of IP messages. In other service elements, this pragmatic result can be treated as effective support of this service element. Original Encoded Information Types Indication Supported as a new RFC 822 header (Original-Encoded-Information-Types:). Submission Time Stamp Indication Supported. Typed Body Some types supported. IA5 is fully supported. ForwardedIPMessage is supported, with some loss of information. Other types get some measure of support, dependent on X.400 facilities for conversion to IA5. This
will only be done where content conversion is not
prohibited.
User Capabilities Registration
N/A (local).
2.3.1.2. IPM Service Optional User Facilities
This section describes support for the optional (user selectable) IPM
services as listed in Section 19.9 of X.400 / ISO/IEC 10021- 1,
listed here in the order given. Section 19.9 has cross references to
short definitions of each service.
Additional Physical Rendition
N/A (PDAU).
Alternate Recipient Allowed
Not supported. There is no RFC 822 service equivalent to
prohibition of alternate recipient assignment (e.g., an RFC
822 system may freely send an undeliverable message to a
local postmaster). Thus, the gateway cannot prevent
assignment of alternative recipients on the RFC 822 side.
This service really means giving the user control as to
whether or not an alternate recipient is allowed. This
specification requires transfer of messages to RFC 822
irrespective of this service request, and so this service is
not supported.
Authorising User's Indication
Supported.
Auto-forwarded Indication
Supported as new RFC 822 header (Auto-Forwarded:).
Basic Physical Rendition
N/A (PDAU).
Blind Copy Recipient Indication
Supported.
Body Part Encryption Indication
Supported by use of a new RFC 822 header
(Original-Encoded-Information-Types:), although in most
cases it will not be possible to map the body part in
question.
Content Confidentiality
Not supported.
Content Integrity
Not supported.
Conversion Prohibition
Supported. In this case, only messages with IA5 body parts,
other body parts which contain only IA5, and Forwarded IP
Messages (subject recursively to the same restrictions),
will be mapped.
Conversion Prohibition in Case of Loss of Information
Supported.
Counter Collection
N/A (PDAU).
Counter Collection with Advice
N/A (PDAU).
Cross Referencing Indication
Supported.
Deferred Delivery
N/A (prior). This service should always be provided by the
MTS prior to the gateway. A new RFC 822 header
Deferred-Delivery:) is provided to transfer information on
this service to the recipient.
Deferred Delivery Cancellation
N/A (local).
Delivery Notification
Supported. This is performed at the gateway. Thus, a
notification is sent by the gateway to the originator. If
the 822-MTS protocol is JNT Mail, a notification may also be
sent by the recipient UA.
Delivery via Bureaufax Service
N/A (PDAU).
Designation of Recipient by Directory Name
N/A (local).
Disclosure of Other Recipients
Supported by use of a new RFC 822 header (X400-Recipients:).
This is descriptive information for the RFC 822 recipient,
and is not reverse mappable.
DL Expansion History Indication
Supported by use of a new RFC 822 header
DL-Expansion-History:).
DL Expansion Prohibited
Distribution List means MTS supported distribution list, in
the manner of X.400. This service does not exist in the RFC
822 world. RFC 822 distribution lists should be regarded as
an informal redistribution mechanism, beyond the scope of
this control. Messages will be sent to RFC 822,
irrespective of whether this service is requested.
Theoretically therefore, this service is supported, although
in practice it may appear that it is not supported.
Express Mail Service
N/A (PDAU).
Expiry Date Indication
Supported as new RFC 822 header (Expiry-Date:). In general,
no automatic action can be expected.
Explicit Conversion
N/A (prior).
Forwarded IP Message Indication
Supported, with some loss of information. The message is
forwarded in an RFC 822 body, and so can only be interpreted
visually.
Grade of Delivery Selection
N/A (PDAU)
Importance Indication
Supported as new RFC 822 header (Importance:).
Incomplete Copy Indication
Supported as new RFC 822 header (Incomplete-Copy:).
Language Indication
Supported as new RFC 822 header (Language:).
Latest Delivery Designation
Not supported. A new RFC 822 header (Latest-Delivery-Time:)
is provided, which may be used by the recipient.
Message Flow Confidentiality
Not supported.
Message Origin Authentication
N/A (reception).
Message Security Labelling
Not supported.
Message Sequence Integrity
Not supported.
Multi-Destination Delivery
Supported.
Multi-part Body
Supported, with some loss of information, in that the
structuring cannot be formalised in RFC 822.
Non Receipt Notification Request
Not supported.
Non Repudiation of Delivery
Not supported.
Non Repudiation of Origin
N/A (reception).
Non Repudiation of Submission
N/A (local).
Obsoleting Indication
Supported as new RFC 822 header (Obsoletes:).
Ordinary Mail
N/A (PDAU).
Originator Indication
Supported.
Originator Requested Alternate Recipient
Not supported, but is placed as comment next to address
X400-Recipients:).
Physical Delivery Notification by MHS
N/A (PDAU).
Physical Delivery Notification by PDS
N/A (PDAU).
Physical Forwarding Allowed
Supported by use of a comment in a new RFC 822 header
X400-Recipients:), associated with the recipient in
question.
Physical Forwarding Prohibited
Supported by use of a comment in a new RFC 822 header
X400-Recipients:), associated with the recipient in
question.
Prevention of Non-delivery notification
Supported, as delivery notifications cannot be generated by
RFC 822. In practice, errors will be returned as IP
Messages, and so this service may appear not to be supported
see Non-delivery Notification).
Primary and Copy Recipients Indication
Supported
Probe
Supported at the gateway (i.e., the gateway services the
probe).
Probe Origin Authentication
N/A (reception).
Proof of Delivery
Not supported.
Proof of Submission
N/A (local).
Receipt Notification Request Indication
Not supported.
Redirection Allowed by Originator
Redirection means MTS supported redirection, in the manner
of X.400. This service does not exist in the RFC 822 world.
RFC 822 redirection (e.g., aliasing) should be regarded as
an informal redirection mechanism, beyond the scope of this
control. Messages will be sent to RFC 822, irrespective of
whether this service is requested. Theoretically therefore,
this service is supported, although in practice it may
appear that it is not supported.
Registered Mail
N/A (PDAU).
Registered Mail to Addressee in Person
N/A (PDAU).
Reply Request Indication
Supported as comment next to address.
Replying IP Message Indication
Supported.
Report Origin Authentication
N/A (reception).
Request for Forwarding Address
N/A (PDAU).
Requested Delivery Method
N/A (local). The services required must be dealt with at
submission time. Any such request is made available through
the gateway by use of a comment associated with the
recipient in question.
Return of Content
In principle, this is N/A, as non-delivery notifications are
not supported. In practice, most RFC 822 systems will
return part or all of the content along with the IP Message
indicating an error (see Non-delivery Notification).
Sensitivity Indication
Supported as new RFC 822 header (Sensitivity:).
Special Delivery
N/A (PDAU).
Stored Message Deletion
N/A (MS).
Stored Message Fetching
N/A (MS).
Stored Message Listing
N/A (MS).
Stored Message Summary
N/A (MS).
Subject Indication
Supported.
Undeliverable Mail with Return of Physical Message
N/A (PDAU).
Use of Distribution List
In principle this applies only to X.400 supported
distribution lists (see DL Expansion Prohibited).
Theoretically, this service is N/A (prior). In practice,
because of informal RFC 822 lists, this service can be
regarded as supported.
2.3.2. Reception by X.400
2.3.2.1. Standard Mandatory Services
The following standard IPM mandatory user facilities are required
for reception of RFC 822 originated mail by an X.400 UA.
Content Type Indication
Delivery Time Stamp Indication
IP Message Identification
Message Identification
Non-delivery Notification
Original Encoded Information Types Indication
Submission Time Stamp Indication
Typed Body
2.3.2.2. Standard Optional Services
The following standard IPM optional user facilities are required for
reception of RFC 822 originated mail by an X.400 UA.
Authorising User's Indication
Blind Copy Recipient Indication
Cross Referencing Indication
Originator Indication
Primary and Copy Recipients Indication
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.
(page 24 continued on part 2)