RFCs in HTML Format

RFC 1327

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
Table of Contents

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

Hardcastle-Kille                                                [Page 1]

RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992 1.11 - Acknowledgements .............................. 9 2 - Service Elements .............................. 10 2.1 - The Notion of Service Across a Gateway ........ 10 2.2 - RFC 822 ....................................... 11 2.3 - X.400 ......................................... 15 3 - Basic Mappings ................................ 24 3.1 - Notation ...................................... 24 3.2 - ASCII and IA5 ................................. 26 3.3 - Standard Types ................................ 26 3.4 - Encoding ASCII in Printable String ............ 28 4 - Addressing .................................... 30 4.1 - A textual representation of MTS.ORAddress ..... 30 4.2 - Basic Representation .......................... 31 4.3 - EBNF.822-address <-> MTS.ORAddress ............ 36 4.4 - Repeated Mappings ............................. 48 4.5 - Directory Names ............................... 50 4.6 - MTS Mappings .................................. 50 4.7 - IPMS Mappings ................................. 55 5 - Detailed Mappings ............................. 59 5.1 - RFC 822 -> X.400 .............................. 59 5.2 - Return of Contents ............................ 67 5.3 - X.400 -> RFC 822 .............................. 67 Appendix A - Mappings Specific to SMTP ..................... 91 Appendix B - Mappings specific to the JNT Mail ............. 91 1 - Introduction .................................. 91 2 - Domain Ordering ............................... 91 3 - Addressing .................................... 91 4 - Acknowledge-To: .............................. 91 5 - Trace ......................................... 92 6 - Timezone specification ........................ 92 7 - Lack of 822-MTS originator specification ...... 92 Appendix C - Mappings specific to UUCP Mail ................ 93 Appendix D - Object Identifier Assignment .................. 94 Appendix E - BNF Summary ................................... 94 Appendix F - Format of address mapping tables .............. 101 1 - Global Mapping Information .................... 101 2 - Syntax Definitions ............................ 102 3 - Table Lookups ................................. 103 4 - Domain -> O/R Address format .................. 104 5 - O/R Address -> Domain format .................. 104 6 - Domain -> O/R Address of Gateway table ........ 104 Appendix G - Mapping with X.400(1984) ...................... 105 Appendix H - RFC 822 Extensions for X.400 access ........... 106 Appendix I - Conformance ................................... 106 Appendix J - Change History: RFC 987, 1026, 1138, 1148 ..... 107 1 - Introduction .................................. 108 2 - Service Elements .............................. 108 3 - Basic Mappings ................................ 108 Hardcastle-Kille [Page 2]
RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992 4 - Addressing .................................... 108 5 - Detailed Mappings ............................. 109 6 - Appendices .................................... 109 Appendix K - Change History: RFC 1148 to this Document ..... 109 1 - General ....................................... 109 2 - Basic Mappings ................................ 110 3 - Addressing .................................... 110 4 - Detailed Mappings ............................. 110 5 - Appendices .................................... 110 References ................................................. 111 Security Considerations .................................... 113 Author's Address ........................................... 113 Chapter 1 -- Overview 1.1. X.400 This document relates to the CCITT 1988 X.400 Series Recommendations / ISO IEC 10021 on the Message Oriented Text Interchange Service (MOTIS). This ISO/CCITT standard is referred to in this document as "X.400", which is a convenient shorthand. Any reference to the 1984 CCITT Recommendations will be explicit. X.400 defines an Interpersonal Messaging System (IPMS), making use of a store and forward Message Transfer System. This document relates to the IPMS, and not to wider application of X.400. It is expected that X.400 will be implemented very widely. 1.2. RFC 822 RFC 822 evolved as a messaging standard on the DARPA (the US Defense Advanced Research Projects Agency) Internet. It specifies and end to end message format. It is used in conjunction with a number of different message transfer protocol environments. SMTP Networks On the DARPA Internet and other TCP/IP networks, RFC 822 is used in conjunction with two other standards: RFC 821, also known as Simple Mail Transfer Protocol (SMTP) [Postel82a], and RFC 920 which is a Specification for domains and a distributed name service [Postel84a]. UUCP Networks UUCP is the UNIX to UNIX CoPy protocol, which is usually used over dialup telephone networks to provide a simple message transfer mechanism. There are some extensions to RFC 822, particularly in the addressing. They use domains which conform to RFC 920, but not the corresponding domain nameservers [Horton86a]. Hardcastle-Kille [Page 3]
RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992 Bitnet Some parts of Bitnet and related networks use RFC 822 related protocols, with EBCDIC encoding. JNT Mail Networks A number of X.25 networks, particularly those associated with the UK Academic Community, use the JNT (Joint Network Team) Mail Protocol, also known as Greybook [Kille84a]. This is used with domains and name service specified by the JNT NRS (Name Registration Scheme) [Larmouth83a]. The mappings specified here are appropriate for all of these networks. 1.3. The need for conversion There is a large community using RFC 822 based protocols for mail services, who will wish to communicate with users of the IPMS provided by X.400 systems. This will also be a requirement in cases where communities intend to make a transition to use of an X.400 IPMS, as conversion will be needed to ensure a smooth service transition. It is expected that there will be more than one gateway, and this specification will enable them to behave in a consistent manner. Note that the term gateway is used to describe a component performing the protocol mappings between RFC 822 and X.400. This is standard usage amongst mail implementors, but should be noted carefully by transport and network service implementors. Consistency between gateways is desirable to provide: 1. Consistent service to users. 2. The best service in cases where a message passes through multiple gateways. 1.4. General approach There are a number of basic principles underlying the details of the specification. These principles are goals, and are not achieved in all aspects of the specification. 1. The specification should be pragmatic. There should not be a requirement for complex mappings for "Academic" reasons. Complex mappings should not be required to support trivial additional functionality. 2. Subject to 1), functionality across a gateway should be as high as possible. Hardcastle-Kille [Page 4]
RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992 3. It is always a bad idea to lose information as a result of any transformation. Hence, it is a bad idea for a gateway to discard information in the objects it processes. This includes requested services which cannot be fully mapped. 4. All mail gateways actually operate at exactly one level above the layer on which they conceptually operate. This implies that the gateway must not only be cognisant of the semantics of objects at the gateway level, but also be cognisant of higher level semantics. If meaningful transformation of the objects that the gateway operates on is to occur, then the gateway needs to understand more than the objects themselves. 5. Subject to 1), the specification should be reversible. That is, a double transformation should bring you back to where you started. 1.5. Gatewaying Model 1.5.1. X.400 X.400 defines the IPMS Abstract Service in X.420/ISO 10021-7, [CCITT/ISO88b] which comprises of three basic services: 1. Origination 2. Reception 3. Management Management is a local interaction between the user and the IPMS, and is therefore not relevant to gatewaying. The first two services consist of operations to originate and receive the following two objects: 1. IPM (Interpersonal Message). This has two components: a heading, and a body. The body is structured as a sequence of body parts, which may be basic components (e.g., IA5 text, or G3 fax), or IP Messages. The heading consists of fields containing end to end user information, such as subject, primary recipients (To:), and importance. 2. IPN (Inter Personal Notification). A notification about receipt of a given IPM at the UA level. The Origination service also allows for origination of a probe, which is an object to test whether a given IPM could be correctly received. Hardcastle-Kille [Page 5]
RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992 The Reception service also allows for receipt of Delivery Reports DR), which indicate delivery success or failure. These IPMS Services utilise the Message Transfer (MT) Abstract Service [CCITT/ISO88c]. The MT Abstract Service provides the following three basic services: 1. Submission (used by IPMS Origination) 2. Delivery (used by IPMS Reception) 3. Administration (used by IPMS Management) Administration is a local issue, and so does not affect this standard. Submission and delivery relate primarily to the MTS Message (comprising Envelope and Content), which carries an IPM or IPN (or other uninterpreted contents). There is also an Envelope, which includes an ID, an originator, and a list of recipients. Submission also includes the probe service, which supports the IPMS Probe. Delivery also includes Reports, which indicate whether a given MTS Message has been delivered or not. The MTS is REFINED into the MTA (Message Transfer Agent) Service, which defines the interaction between MTAs, along with the procedures for distributed operation. This service provides for transfer of MTS Messages, Probes, and Reports. 1.5.2. RFC 822 RFC 822 is based on the assumption that there is an underlying service, which is here called the 822-MTS service. The 822-MTS service provides three basic functions: 1. Identification of a list of recipients. 2. Identification of an error return address. 3. Transfer of an RFC 822 message. It is possible to achieve 2) within the RFC 822 header. Some 822-MTS protocols, in particular SMTP, can provide additional functionality, but as these are neither mandatory in SMTP, nor available in other 822-MTS protocols, they are not considered here. Details of aspects specific to two 822-MTS protocols are given in Appendices B and C. An RFC 822 message consists of a header, and content which is uninterpreted ASCII text. The header is divided into fields, which are the protocol elements. Most of these fields are analogous to P2 heading fields, although some are analogous to MTS Service Elements Hardcastle-Kille [Page 6]
RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992 or MTA Service Elements. 1.5.3. The Gateway Given this functional description of the two services, the functional nature of a gateway can now be considered. It would be elegant to consider the 822-MTS service mapping onto the MTS Service Elements and RFC 822 mapping onto an IPM, but reality just does not fit. Another elegant approach would be to treat this document as the definition of an X.400 Access Unit (AU). Again, reality does not fit. It is necessary to consider that the IPM format definition, the IPMS Service Elements, the MTS Service Elements, and MTA Service Elements on one side are mapped into RFC 822 + 822-MTS on the other in a slightly tangled manner. The details of the tangle will be made clear in Chapter 5. Access to the MTA Service Elements is minimised. The following basic mappings are thus defined. When going from RFC 822 to X.400, an RFC 822 message and the associated 822-MTS information is always mapped into an IPM (MTA, MTS, and IPMS Services). Going from X.400 to RFC 822, an RFC 822 message and the associated 822-MTS information may be derived from: 1. A Report (MTA, and MTS Services) 2. An IPN (MTA, MTS, and IPMS services) 3. An IPM (MTA, MTS, and IPMS services) Probes (MTA Service) must be processed by the gateway, as discussed in Chapter 5. MTS Messages containing Content Types other than those defined by the IPMS are not mapped by the gateway, and should be rejected at the gateway. 1.5.4. Repeated Mappings The primary goal of this specification is to support single mappings, so that X.400 and RFC 822 users can communicate with maximum functionality. The mappings specified here are designed to work where a message traverses multiple times between X.400 and RFC 822. This is often essential, particularly in the case of distribution lists. However, in general, this will lead to a level of service which is the lowest common denominator (approximately the services offered by RFC 822). Some RFC 822 networks may wish to use X.400 as an interconnection mechanism (typically for policy reasons), and this is fully supported. Hardcastle-Kille [Page 7]
RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992 Where an X.400 messages transfers to RFC 822 and then back to X.400, there is no expectation of X.400 services which do not have an equivalent service in standard RFC 822 being preserved - although this may be possible in some cases. 1.6. X.400 (1984) Much of this work is based on the initial specification of RFC 987 and in its addendum RFC 1026, which defined a mapping between X.400(1984) and RFC 822. A basic decision is that the mapping defined in this document is to the full 1988 version of X.400, and not to a 1984 compatible subset. New features of X.400(1988) can be used to provide a much cleaner mapping than that defined in RFC 987. This is important, to give good support to communities which will utilise full X.400 at an early date. To interwork with 1984 systems, Appendix G shall be followed. If a message is being transferred to an X.400(1984) system by way of X.400(1988) MTA it will give a slightly better service to follow the rules of Appendix G. 1.7. Compatibility with previous versions The changes between this and older versions of the document are given in Appendices I and J. These are RFCs 987, 1026, 1138, and 1148. This document is a revision of RFC 1148 [Kille90a]. As far as possible, changes have been made in a compatible fashion. 1.8. Aspects not covered There have been a number of cases where RFC 987 was used in a manner which was not intended. This section is to make clear some limitations of scope. In particular, this specification does not specify: - 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 Hardcastle-Kille [Page 8]
RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992 all X.400 services. Thus, it will be a poor choice for X.400 implementors to use RFC 987(88) as an interface - there are too many aspects of X.400 which cannot be accessed through it. If a text interface is desired, a specification targeted at X.400, without RFC 822 restrictions, would be more appropriate. Some optional and limited extensions in this area have proved useful, and are defined in Appendix H. 1.9. Subsetting This proposal specifies a mapping which is appropriate to preserve services in existing RFC 822 communities. Implementations and specifications which subset this specification are strongly discouraged. 1.10. Document Structure This document has five chapters: 1. Overview - this chapter. 2. Service Elements - This describes the (end user) services mapped by a gateway. 3. Basic mappings - This describes some basic notation used in Chapters 3-5, the mappings between character sets, and some fundamental protocol elements. 4. Addressing - This considers the mapping between X.400 O/R names and RFC 822 addresses, which is a fundamental gateway component. 5. Detailed Mappings - This describes the details of all other mappings. There are also eleven appendices. WARNING: THE REMAINDER OF THIS SPECIFICATION IS TECHNICALLY DETAILED. IT WILL NOT MAKE SENSE, EXCEPT IN THE CONTEXT OF RFC 822 AND X.400 (1988). DO NOT ATTEMPT TO READ THIS DOCUMENT UNLESS YOU ARE FAMILIAR WITH THESE SPECIFICATIONS. 1.11. Acknowledgements The work in this specification was substantially based on RFC 987 and RFC 1148, which had input from many people, who are credited in the respective documents. Hardcastle-Kille [Page 9]
RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992 A number of comments from people on RFC 1148 lead to this document. In particular, there were comments and suggestions from: Maurice Abraham (HP); Harald Alvestrand (Sintef); Peter Cowen (X-Tel); Jim Craigie (JNT); Ella Gardener (MITRE); Christian Huitema (Inria); Erik Huizer (SURFnet); Neil Jones DEC); Ignacio Martinez (IRIS); Julian Onions (X-Tel); Simon Poole (SWITCH); Clive Roberts (Data General); Pete Vanderbilt SUN); Alan Young (Concurrent). Chapter 2 - Service Elements This chapter considers the services offered across a gateway built according to this specification. It gives a view of the functionality provided by such a gateway for communication with users in the opposite domain. This chapter considers service mappings in the context of SINGLE transfers only, and not repeated mappings through multiple gateways. 2.1. The Notion of Service Across a Gateway RFC 822 and X.400 provide a number of services to the end user. This chapter describes the extent to which each service can be supported across an X.400 <-> RFC 822 gateway. The cases considered are single transfers across such a gateway, although the problems of multiple crossings are noted where appropriate. 2.1.1. Origination of Messages When a user originates a message, a number of services are available. Some of these imply actions (e.g., delivery to a recipient), and some are insertion of known data (e.g., specification of a subject field). This chapter describes, for each offered service, to what extent it is supported for a recipient accessed through a gateway. There are three levels of support: Supported The corresponding protocol elements map well, and so the service can be fully provided. Not Supported The service cannot be provided, as there is a complete mismatch. Partial Support The service can be partially fulfilled. In the first two cases, the service is simply marked as Supported" or "Not Supported". Some explanation may be given if there are additional implications, or the (non) support is not intuitive. For Hardcastle-Kille [Page 10]
RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992 partial support, the level of partial support is summarised. Where partial support is good, this will be described by a phrase such as "Supported by use of.....". A common case of this is where the service is mapped onto a non- standard service on the other side of the gateway, and this would have lead to support if it had been a standard service. In many cases, this is equivalent to support. For partial support, an indication of the mechanism is given, in order to give a feel for the level of support provided. Note that this is not a replacement for Chapter 5, where the mapping is fully specified. If a service is described as supported, this implies: - 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). Hardcastle-Kille [Page 11]
RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992 This can be regarded as partial support, as it makes the information available to any X.400 implementations which are interested in these services. Communities which require significant RFC 822 interworking are recommended to require that their X.400 User Agents are able to display these heading extensions. Support for the various service elements (headers) is now listed. Date: Supported. From: Supported. For messages where there is also a sender field, the mapping is to "Authorising Users Indication", which has subtly different semantics to the general RFC 822 usage of From:. Sender: Supported. Reply-To: Supported. To: Supported. Cc: Supported. Bcc: Supported. Message-Id: Supported. In-Reply-To: Supported, for a single reference. Where multiple references are given, partial support is given by mapping to "Cross Referencing Indication". This gives similar semantics. References: Supported. Keywords: Supported by use of a heading extension. Subject: Supported. Comments: Supported by use of an extra body part. Hardcastle-Kille [Page 12]
RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992 Encrypted: Supported by use of a heading extension. Resent-* Supported by use of a heading extension. Note that addresses in these fields are mapped onto text, and so are not accessible to the X.400 user as addresses. In principle, fuller support would be possible by mapping onto a forwarded IP Message, but this is not suggested. Other Fields In particular X-* fields, and "illegal" fields in common usage (e.g., "Fruit-of-the-day:") are supported by use of heading extensions. 2.2.2. Reception by RFC 822 This considers reception by an RFC 822 User Agent of a message originated in an X.400 system and transferred across a gateway. The following standard services (headers) may be present in such a message: Date: From: Sender: Reply-To: To: Cc: Bcc: Message-Id: In-Reply-To: References: Subject: The following non-standard services (headers) may be present. These are defined in more detail in Chapter 5 (5.3.4, 5.3.6, 5.3.7): Hardcastle-Kille [Page 13]
RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992 Autoforwarded: Content-Identifier: Conversion: Conversion-With-Loss: Delivery-Date: Discarded-X400-IPMS-Extensions: Discarded-X400-MTS-Extensions: DL-Expansion-History: Deferred-Delivery: Expiry-Date: Importance: Incomplete-Copy: Language: Latest-Delivery-Time: Message-Type: Obsoletes: Original-Encoded-Information-Types: Originator-Return-Address: Priority: Reply-By: Requested-Delivery-Method: Sensitivity: X400-Content-Type: X400-MTS-Identifier: Hardcastle-Kille [Page 14]
RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992 X400-Originator: X400-Received: X400-Recipients: 2.3. X.400 2.3.1. Origination in X.400 When mapping services from X.400 to RFC 822 which are not supported by RFC 822, new RFC 822 headers are defined. It is intended that these fields will be registered, and that co- operating RFC 822 systems may use them. Where these new fields are used, and no system action is implied, the service can be regarded as being partially supported. Chapter 5 describes how to map X.400 services onto these new headers. Other elements are provided, in part, by the gateway as they cannot be provided by RFC 822. Some service elements are marked N/A (not applicable). There are five cases, which are marked with different comments: N/A (local) These elements are only applicable to User Agent / Message Transfer Agent interaction and so they cannot apply to RFC 822 recipients. N/A (PDAU) These service elements are only applicable where the recipient is reached by use of a Physical Delivery Access Unit (PDAU), and so do not need to be mapped by the gateway. N/A (reception) These services are only applicable for reception. N/A (prior) If requested, this service must be performed prior to the gateway. N/A (MS) These services are only applicable to Message Store (i.e., a local service). Finally, some service elements are not supported. In particular, the new security services are not mapped onto RFC 822. Unless otherwise indicated, the behaviour of service elements marked as not supported will depend on the criticality marking supplied by the user. If the element is marked as critical for transfer or delivery, a non- Hardcastle-Kille [Page 15]
RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992 delivery notification will be generated. Otherwise, the service request will be ignored. Basic Interpersonal Messaging Service These are the mandatory IPM services as listed in Section 19.8 of X.400 / ISO/IEC 10021-1, listed here in the order given. Section 19.8 has cross references to short definitions of each service. Access management N/A (local). Content Type Indication Supported by a new RFC 822 header (Content-Type:). Converted Indication Supported by a new RFC 822 header (X400-Received:). Delivery Time Stamp Indication N/A (reception). IP Message Identification Supported. Message Identification Supported, by use of a new RFC 822 header (X400-MTS-Identifier). This new header is required, as X.400 has two message-ids whereas RFC 822 has only one (see previous service). Non-delivery Notification Not supported, although in general an RFC 822 system will return error reports by use of IP messages. In other service elements, this pragmatic result can be treated as effective support of this service element. Original Encoded Information Types Indication Supported as a new RFC 822 header (Original-Encoded-Information-Types:). Submission Time Stamp Indication Supported. Typed Body Some types supported. IA5 is fully supported. ForwardedIPMessage is supported, with some loss of information. Other types get some measure of support, dependent on X.400 facilities for conversion to IA5. This Hardcastle-Kille [Page 16]
RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992 will only be done where content conversion is not prohibited. User Capabilities Registration N/A (local). IPM Service Optional User Facilities This section describes support for the optional (user selectable) IPM services as listed in Section 19.9 of X.400 / ISO/IEC 10021- 1, listed here in the order given. Section 19.9 has cross references to short definitions of each service. Additional Physical Rendition N/A (PDAU). Alternate Recipient Allowed Not supported. There is no RFC 822 service equivalent to prohibition of alternate recipient assignment (e.g., an RFC 822 system may freely send an undeliverable message to a local postmaster). Thus, the gateway cannot prevent assignment of alternative recipients on the RFC 822 side. This service really means giving the user control as to whether or not an alternate recipient is allowed. This specification requires transfer of messages to RFC 822 irrespective of this service request, and so this service is not supported. Authorising User's Indication Supported. Auto-forwarded Indication Supported as new RFC 822 header (Auto-Forwarded:). Basic Physical Rendition N/A (PDAU). Blind Copy Recipient Indication Supported. Body Part Encryption Indication Supported by use of a new RFC 822 header (Original-Encoded-Information-Types:), although in most cases it will not be possible to map the body part in question. Content Confidentiality Not supported. Hardcastle-Kille [Page 17]
RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992 Content Integrity Not supported. Conversion Prohibition Supported. In this case, only messages with IA5 body parts, other body parts which contain only IA5, and Forwarded IP Messages (subject recursively to the same restrictions), will be mapped. Conversion Prohibition in Case of Loss of Information Supported. Counter Collection N/A (PDAU). Counter Collection with Advice N/A (PDAU). Cross Referencing Indication Supported. Deferred Delivery N/A (prior). This service should always be provided by the MTS prior to the gateway. A new RFC 822 header Deferred-Delivery:) is provided to transfer information on this service to the recipient. Deferred Delivery Cancellation N/A (local). Delivery Notification Supported. This is performed at the gateway. Thus, a notification is sent by the gateway to the originator. If the 822-MTS protocol is JNT Mail, a notification may also be sent by the recipient UA. Delivery via Bureaufax Service N/A (PDAU). Designation of Recipient by Directory Name N/A (local). Disclosure of Other Recipients Supported by use of a new RFC 822 header (X400-Recipients:). This is descriptive information for the RFC 822 recipient, and is not reverse mappable. Hardcastle-Kille [Page 18]
RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992 DL Expansion History Indication Supported by use of a new RFC 822 header DL-Expansion-History:). DL Expansion Prohibited Distribution List means MTS supported distribution list, in the manner of X.400. This service does not exist in the RFC 822 world. RFC 822 distribution lists should be regarded as an informal redistribution mechanism, beyond the scope of this control. Messages will be sent to RFC 822, irrespective of whether this service is requested. Theoretically therefore, this service is supported, although in practice it may appear that it is not supported. Express Mail Service N/A (PDAU). Expiry Date Indication Supported as new RFC 822 header (Expiry-Date:). In general, no automatic action can be expected. Explicit Conversion N/A (prior). Forwarded IP Message Indication Supported, with some loss of information. The message is forwarded in an RFC 822 body, and so can only be interpreted visually. Grade of Delivery Selection N/A (PDAU) Importance Indication Supported as new RFC 822 header (Importance:). Incomplete Copy Indication Supported as new RFC 822 header (Incomplete-Copy:). Language Indication Supported as new RFC 822 header (Language:). Latest Delivery Designation Not supported. A new RFC 822 header (Latest-Delivery-Time:) is provided, which may be used by the recipient. Message Flow Confidentiality Not supported. Hardcastle-Kille [Page 19]
RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992 Message Origin Authentication N/A (reception). Message Security Labelling Not supported. Message Sequence Integrity Not supported. Multi-Destination Delivery Supported. Multi-part Body Supported, with some loss of information, in that the structuring cannot be formalised in RFC 822. Non Receipt Notification Request Not supported. Non Repudiation of Delivery Not supported. Non Repudiation of Origin N/A (reception). Non Repudiation of Submission N/A (local). Obsoleting Indication Supported as new RFC 822 header (Obsoletes:). Ordinary Mail N/A (PDAU). Originator Indication Supported. Originator Requested Alternate Recipient Not supported, but is placed as comment next to address X400-Recipients:). Physical Delivery Notification by MHS N/A (PDAU). Physical Delivery Notification by PDS N/A (PDAU). Hardcastle-Kille [Page 20]
RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992 Physical Forwarding Allowed Supported by use of a comment in a new RFC 822 header X400-Recipients:), associated with the recipient in question. Physical Forwarding Prohibited Supported by use of a comment in a new RFC 822 header X400-Recipients:), associated with the recipient in question. Prevention of Non-delivery notification Supported, as delivery notifications cannot be generated by RFC 822. In practice, errors will be returned as IP Messages, and so this service may appear not to be supported see Non-delivery Notification). Primary and Copy Recipients Indication Supported Probe Supported at the gateway (i.e., the gateway services the probe). Probe Origin Authentication N/A (reception). Proof of Delivery Not supported. Proof of Submission N/A (local). Receipt Notification Request Indication Not supported. Redirection Allowed by Originator Redirection means MTS supported redirection, in the manner of X.400. This service does not exist in the RFC 822 world. RFC 822 redirection (e.g., aliasing) should be regarded as an informal redirection mechanism, beyond the scope of this control. Messages will be sent to RFC 822, irrespective of whether this service is requested. Theoretically therefore, this service is supported, although in practice it may appear that it is not supported. Registered Mail N/A (PDAU). Hardcastle-Kille [Page 21]
RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992 Registered Mail to Addressee in Person N/A (PDAU). Reply Request Indication Supported as comment next to address. Replying IP Message Indication Supported. Report Origin Authentication N/A (reception). Request for Forwarding Address N/A (PDAU). Requested Delivery Method N/A (local). The services required must be dealt with at submission time. Any such request is made available through the gateway by use of a comment associated with the recipient in question. Return of Content In principle, this is N/A, as non-delivery notifications are not supported. In practice, most RFC 822 systems will return part or all of the content along with the IP Message indicating an error (see Non-delivery Notification). Sensitivity Indication Supported as new RFC 822 header (Sensitivity:). Special Delivery N/A (PDAU). Stored Message Deletion N/A (MS). Stored Message Fetching N/A (MS). Stored Message Listing N/A (MS). Stored Message Summary N/A (MS). Subject Indication Supported. Hardcastle-Kille [Page 22]
RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992 Undeliverable Mail with Return of Physical Message N/A (PDAU). Use of Distribution List In principle this applies only to X.400 supported distribution lists (see DL Expansion Prohibited). Theoretically, this service is N/A (prior). In practice, because of informal RFC 822 lists, this service can be regarded as supported. 2.3.2. Reception by X.400 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 Standard Optional Services The following standard IPM optional user facilities are required for reception of RFC 822 originated mail by an X.400 UA. Authorising User's Indication Blind Copy Recipient Indication Cross Referencing Indication Originator Indication Primary and Copy Recipients Indication Hardcastle-Kille [Page 23]
RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992 Replying IP Message Indication Subject Indication New Services A new service "RFC 822 Header Field" is defined using the extension facilities. This allows for any RFC 822 header field to be represented. It may be present in RFC 822 originated messages, which are received by an X.400 UA. Chapter 3 Basic Mappings 3.1. Notation The X.400 protocols are encoded in a structured manner according to ASN.1, whereas RFC 822 is text encoded. To define a detailed mapping, it is necessary to refer to detailed protocol elements in each format. A notation to achieve this is described in this section. 3.1.1. RFC 822 Structured text is defined according to the Extended Backus Naur Form (EBNF) defined in Section 2 of RFC 822 [Crocker82a]. In the EBNF definitions used in this specification, the syntax rules given in Appendix D of RFC 822 are assumed. When these EBNF tokens are referred to outside an EBNF definition, they are identified by the string "822." appended to the beginning of the string (e.g., 822.addr-spec). Additional syntax rules, to be used throughout this specification, are defined in this chapter. The EBNF is used in two ways. 1. To describe components of RFC 822 messages (or of 822-MTS components). In this case, the lexical analysis defined in Section 3 of RFC 822 shall be used. When these new EBNF tokens are referred to outside an EBNF definition, they are identified by the string "EBNF." appended to the beginning of the string (e.g., EBNF.importance). 2. To describe the structure of IA5 or ASCII information not in an RFC 822 message. In these cases, tokens will either be self delimiting, or be delimited by self delimiting tokens. Comments and LWSP are not used as delimiters, except for the following cases, where LWSP may be inserted according to RFC 822 rules. Hardcastle-Kille [Page 24]
RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992 - Around the ":" in all headers - EBNF.labelled-integer - EBNF.object-identifier - EBNF.encoded-info RFC 822 folding rules are applied to all headers. 3.1.2. ASN.1 An element is referred to with the following syntax, defined in EBNF: element = service "." definition *( "." definition ) service = "IPMS" / "MTS" / "MTA" definition = identifier / context identifier = ALPHA *< ALPHA or DIGIT or "-" > context = "[" 1*DIGIT "]" The EBNF.service keys are shorthand for the following service specifications: IPMS IPMSInformationObjects defined in Annex E of X.420 / ISO 10021-7. MTS MTSAbstractService defined in Section 9 of X.411 / ISO 10021-4. MTA MTAAbstractService defined in Section 13 of X.411 / ISO 10021-4. The first EBNF.identifier identifies a type or value key in the context of the defined service specification. Subsequent EBNF.identifiers identify a value label or type in the context of the first identifier (SET or SEQUENCE). EBNF.context indicates a context tag, and is used where there is no label or type to uniquely identify a component. The special EBNF.identifier keyword "value" is used to denote an element of a sequence. For example, IPMS.Heading.subject defines the subject element of the IPMS heading. The same syntax is also used to refer to element values. For example, MTS.EncodedInformationTypes.[0].g3Fax refers to a value of MTS.EncodedInformationTypes.[0] . Hardcastle-Kille [Page 25]
RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992 3.2. ASCII and IA5 A gateway will interpret all IA5 as ASCII. Thus, mapping between these forms is conceptual. 3.3. Standard Types There is a need to convert between ASCII text, and some of the types defined in ASN.1 [CCITT/ISO88d]. For each case, an EBNF syntax definition is given, for use in all of this specification, which leads to a mapping between ASN.1, and an EBNF construct. All EBNF syntax definitions of ASN.1 types are in lower case, whereas ASN.1 types are referred to with the first letter in upper case. Except as noted, all mappings are symmetrical. 3.3.1. Boolean Boolean is encoded as: boolean = "TRUE" / "FALSE" 3.3.2. NumericString NumericString is encoded as: numericstring = *DIGIT 3.3.3. PrintableString PrintableString is a restricted IA5String defined as: printablestring = *( ps-char ) ps-restricted-char = 1DIGIT / 1ALPHA / " " / "'" / "+" / "," / "-" / "." / "/" / ":" / "=" / "?" ps-delim = "(" / ")" ps-char = ps-delim / ps-restricted-char This can be used to represent real printable strings in EBNF. 3.3.4. T.61String In cases where T.61 strings are only used for conveying human interpreted information, the aim of a mapping is to render the characters appropriately in the remote character set, rather than to maximise reversibility. For these cases, the mappings to IA5 defined in CCITT Recommendation X.408 (1988) shall be used [CCITT/ISO88a]. These will then be encoded in ASCII. Hardcastle-Kille [Page 26]
RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992 There is also a need to represent Teletex Strings in ASCII, for some aspects of O/R Address. For these, the following encoding is used: teletex-string = *( ps-char / t61-encoded ) t61-encoded = "{" 1* t61-encoded-char "}" t61-encoded-char = 3DIGIT Common characters are mapped simply. Other octets are mapped using a quoting mechanism similar to the printable string mechanism. Each octet is represented as 3 decimal digits. There are a number of places where a string may have a Teletex and/or Printable String representation. The following BNF is used to represent this. teletex-and-or-ps = [ printablestring ] [ "*" teletex-string ] The natural mapping is restricted to EBNF.ps-char, in order to make the full BNF easier to parse. 3.3.5. UTCTime Both UTCTime and the RFC 822 822.date-time syntax contain: Year (lowest two digits), Month, Day of Month, hour, minute, second (optional), and Timezone. 822.date-time also contains an optional day of the week, but this is redundant. Therefore a symmetrical mapping can be made between these constructs. Note: In practice, a gateway will need to parse various illegal variants on 822.date-time. In cases where 822.date-time cannot be parsed, it is recommended that the derived UTCTime is set to the value at the time of translation. When mapping to X.400, the UTCTime format which specifies the timezone offset shall be used. When mapping to RFC 822, the 822.date-time format shall include a numeric timezone offset (e.g., +0000). When mapping time values, the timezone shall be preserved as specified. The date shall not be normalised to any other timezone. 3.3.6. Integer A basic ASN.1 Integer will be mapped onto EBNF.numericstring. In many cases ASN.1 will enumerate Integer values or use ENUMERATED. An EBNF encoding labelled-integer is provided. When mapping from EBNF to Hardcastle-Kille [Page 27]
RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992 ASN.1, only the integer value is mapped, and the associated text is discarded. When mapping from ASN.1 to EBNF, addition of an appropriate text label is strongly encouraged. labelled-integer ::= [ key-string ] "(" numericstring ")" key-string = *key-char key-char = <a-z, A-Z, 0-9, and "-"> 3.3.7. Object Identifier Object identifiers are represented in a form similar to that given in ASN.1. The order is the same as for ASN.1 (big-endian). The numbers are mandatory, and used when mapping from the ASCII to ASN.1. The key-strings are optional. It is recommended that as many strings as possible are generated when mapping from ASN.1 to ASCII, to facilitate user recognition. object-identifier ::= oid-comp object-identifier | oid-comp oid-comp ::= [ key-string ] "(" numericstring ")" An example representation of an object identifier is: joint-iso-ccitt(2) mhs (6) ipms (1) ep (11) ia5-text (0) or (2) (6) (1)(11)(0) 3.4. Encoding ASCII in Printable String Some information in RFC 822 is represented in ASCII, and needs to be mapped into X.400 elements encoded as printable string. For this reason, a mechanism to represent ASCII encoded as PrintableString is needed. A structured subset of EBNF.printablestring is now defined. This shall be used to encode ASCII in the PrintableString character set. Hardcastle-Kille [Page 28]
RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992 ps-encoded = *( ps-restricted-char / ps-encoded-char ) ps-encoded-char = "(a)" ; (@) / "(p)" ; (%) / "(b)" ; (!) / "(q)" ; (") / "(u)" ; (_) / "(l)" ; "(" / "(r)" ; ")" / "(" 3DIGIT ")" The 822.3DIGIT in EBNF.ps-encoded-char must have range 0-127, and is interpreted in decimal as the corresponding ASCII character. Special encodings are given for: at sign (@), percent (%), exclamation mark/bang (!), double quote ("), underscore (_), left bracket ((), and right bracket ()). These characters, with the exception of round brackets, are not included in PrintableString, but are common in RFC 822 addresses. The abbreviations will ease specification of RFC 822 addresses from an X.400 system. These special encodings shall be interpreted in a case insensitive manner, but always generated in lower case. A reversible mapping between PrintableString and ASCII can now be defined. The reversibility means that some values of printable string (containing round braces) cannot be generated from ASCII. Therefore, this mapping must only be used in cases where the printable strings may only be derived from ASCII (and will therefore have a restricted domain). For example, in this specification, it is only applied to a Domain Defined Attribute which will have been generated by use of this specification and a value such as "(" would not be possible. To encode ASCII as PrintableString, the EBNF.ps-encoded syntax is used, with all EBNF.ps-restricted-char mapped directly. All other 822.CHAR are encoded as EBNF.ps-encoded-char. To encode PrintableString as ASCII, parse PrintableString as EBNF.ps-encoded, and then reverse the previous mapping. If the PrintableString cannot be parsed, then the mapping is being applied in to an inappropriate value, and an error shall be given to the procedure doing the mapping. In some cases, it may be preferable to pass the printable string through unaltered. Hardcastle-Kille [Page 29]
RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992 Some examples are now given. Note the arrows which indicate asymmetrical mappings: PrintableString ASCII 'a demo.' <-> 'a demo.' foo(a)bar <-> foo@bar (q)(u)(p)(q) <-> "_%" (a) <-> @ (A) -> @ (l)a(r) <-> (a) (126) <-> ~ ( -> ( (l) <-> ( Chapter 4 - Addressing Addressing is probably the trickiest problem of an X.400 <-> RFC 822 gateway. Therefore it is given a separate chapter. This chapter, as a side effect, also defines a textual representation of an X.400 O/R Address. Initially we consider an address in the (human) mail user sense of "what is typed at the mailsystem to reference a mail user". A basic RFC 822 address is defined by the EBNF EBNF.822-address: 822-address = [ route ] addr-spec In an 822-MTS protocol, the originator and each recipient are considered to be defined by such a construct. In an RFC 822 header, the EBNF.822-address is encapsulated in the 822.address syntax rule, and there may also be associated comments. None of this extra information has any semantics, other than to the end user. The basic X.400 O/R Address, used by the MTS for routing, is defined by MTS.ORAddress. In IPMS, the MTS.ORAddress is encapsulated within IPMS.ORDescriptor. It can be seen that RFC 822 822.address must be mapped with IPMS.ORDescriptor, and that RFC 822 EBNF.822-address must be mapped with MTS.ORAddress. 4.1. A textual representation of MTS.ORAddress MTS.ORAddress is structured as a set of attribute value pairs. It is clearly necessary to be able to encode this in ASCII for gatewaying purposes. All components shall be encoded, in order to guarantee return of error messages, and to optimise third party replies. Hardcastle-Kille [Page 30]
RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992 4.2. Basic Representation An O/R Address has a number of structured and unstructured attributes. For each unstructured attribute, a key and an encoding is specified. For structured attributes, the X.400 attribute is mapped onto one or more attribute value pairs. For domain defined attributes, each element of the sequence will be mapped onto a triple (key and two values), with each value having the same encoding. The attributes are as follows, with 1984 attributes given in the first part of the table. For each attribute, a reference is given, consisting of the relevant sections in X.402 / ISO 10021-2, and the extension identifier for 88 only attributes: Attribute (Component) Key Enc Ref Id 84/88 Attributes MTS.CountryName C P 18.3.3 MTS.AdministrationDomainName ADMD P 18.3.1 MTS.PrivateDomainName PRMD P 18.3.21 MTS.NetworkAddress X121 N 18.3.7 MTS.TerminalIdentifier T-ID P 18.3.23 MTS.OrganizationName O P/T 18.3.9 MTS.OrganizationalUnitNames.value OU P/T 18.3.10 MTS.NumericUserIdentifier UA-ID N 18.3.8 MTS.PersonalName PN P/T 18.3.12 MTS.PersonalName.surname S P/T 18.3.12 MTS.PersonalName.given-name G P/T 18.3.12 MTS.PersonalName.initials I P/T 18.3.12 MTS.PersonalName .generation-qualifier GQ P/T 18.3.12 MTS.DomainDefinedAttribute.value DD P/T 18.1 88 Attributes MTS.CommonName CN P/T 18.3.2 1 MTS.TeletexCommonName CN P/T 18.3.2 2 MTS.TeletexOrganizationName O P/T 18.3.9 3 MTS.TeletexPersonalName PN P/T 18.3.12 4 MTS.TeletexPersonalName.surname S P/T 18.3.12 4 MTS.TeletexPersonalName.given-name G P/T 18.3.12 4 MTS.TeletexPersonalName.initials I P/T 18.3.12 4 MTS.TeletexPersonalName .generation-qualifier GQ P/T 18.3.12 4 MTS.TeletexOrganizationalUnitNames .value OU P/T 18.3.10 5 MTS.TeletexDomainDefinedAttribute .value DD P/T 18.1 6 Hardcastle-Kille [Page 31]
RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992 MTS.PDSName PD-SERVICE P 18.3.11 7 MTS.PhysicalDeliveryCountryName PD-C P 18.3.13 8 MTS.PostalCode PD-CODE P 18.3.19 9 MTS.PhysicalDeliveryOfficeName PD-OFFICE P/T 18.3.14 10 MTS.PhysicalDeliveryOfficeNumber PD-OFFICE-NUM P/T 18.3.15 11 MTS.ExtensionORAddressComponents PD-EXT-ADDRESS P/T 18.3.4 12 MTS.PhysicalDeliveryPersonName PD-PN P/T 18.3.17 13 MTS.PhysicalDeliveryOrganizationName PD-O P/T 18.3.16 14 MTS.ExtensionPhysicalDelivery AddressComponents PD-EXT-DELIVERY P/T 18.3.5 15 MTS.UnformattedPostalAddress PD-ADDRESS P/T 18.3.25 16 MTS.StreetAddress PD-STREET P/T 18.3.22 17 MTS.PostOfficeBoxAddress PD-BOX P/T 18.3.18 18 MTS.PosteRestanteAddress PD-RESTANTE P/T 18.3.20 19 MTS.UniquePostalName PD-UNIQUE P/T 18.3.26 20 MTS.LocalPostalAttributes PD-LOCAL P/T 18.3.6 21 MTS.ExtendedNetworkAddress .e163-4-address.number NET-NUM N 18.3.7 22 MTS.ExtendedNetworkAddress .e163-4-address.sub-address NET-SUB N 18.3.7 22 MTS.ExtendedNetworkAddress .psap-address NET-PSAP X 18.3.7 22 MTS.TerminalType T-TY I 18.3.24 23 The following keys identify different EBNF encodings, which are associated with the ASCII representation of MTS.ORAddress. Key Encoding P printablestring N numericstring T teletex-string P/T teletex-and-or-ps I labelled-integer X presentation-address The BNF for presentation-address is taken from the specification "A String Encoding of Presentation Address" [Kille89a]. In most cases, the EBNF encoding maps directly to the ASN.1 encoding of the attribute. There are a few exceptions. In cases where an attribute can be encoded as either a PrintableString or NumericString (Country, ADMD, PRMD), either form is mapped into the BNF. When generating ASN.1, the NumericString encoding shall be used if the string contains only digits. There are a number of cases where the P/T (teletex-and-or-ps) representation is used. Where the key maps to a single attribute, Hardcastle-Kille [Page 32]
RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992 this choice is reflected in the encoding of the attribute (attributes 10-21). For most of the 1984 attributes and common name, there is a printablestring and a teletex variant. This pair of attributes is mapped onto the single component here. This will give a clean mapping for the common cases where only one form of the name is used. Recently, ISO has undertaken work to specify a string form of O/R Address [CCITT/ISO91a]. This has specified a number of string keywords for attributes. As RFC 1148 was an input to this work, many of the keywords are the same. To increase compatability, the following alternative values shall be recognised when mapping from RFC 822 to X.400. These shall not be generated when mapping from X.400 to RFC 822. Keyword Alternative ADMD A PRMD P GQ Q X121 X.121 UA-ID N-ID PD-OFFICE-NUMBER PD-OFFICE NUMBER When mapping from RFC 822 to X.400, the keywords: OU1, OU2, OU3, and OU4, shall be recognised. If these are present, no keyword OU shall be present. These will be treated as ordered values of OU. 4.2.1. Encoding of Personal Name Handling of Personal Name and Teletex Personal Name based purely on the EBNF.standard-type syntax defined above is likely to be clumsy. It seems desirable to utilise the "human" conventions for encoding these components. A syntax is defined, which is designed to provide a clean encoding for the common cases of O/R Address specification where: 1. There is no generational qualifier 2. Initials contain only letters 3. Given Name does not contain full stop ("."), and is at least two characters long. 4. Surname does not contain full stop in the first two characters. 5 If Surname is the only component, it does not contain full stop. Hardcastle-Kille [Page 33]
RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992 The following EBNF is defined: encoded-pn = [ given "." ] *( initial "." ) surname given = 2*<ps-char not including "."> initial = ALPHA surname = printablestring This is used to map from any string containing only printable string characters to an O/R address personal name. To map from a string to O/R Address components, parse the string according to the EBNF. The given name and surname are assigned directly. All EBNF.initial tokens are concatenated without intervening full stops to generate the initials component. For an O/R address which follows the above restrictions, a string is derived in the natural manner. In this case, the mapping will be reversible. For example: GivenName = "Marshall" Surname = "Rose" Maps with "Marshall.Rose" Initials = "MT" Surname = "Rose" Maps with "M.T.Rose" GivenName = "Marshall" Initials = "MT" Surname = "Rose" Maps with "Marshall.M.T.Rose" Note that X.400 suggest that Initials is used to encode ALL initials. Therefore, the defined encoding is "natural" when either GivenName or Initials, but not both, are present. The case where both are present can be encoded, but this appears to be contrived! 4.2.2. Standard Encoding of MTS.ORAddress Given this structure, we can specify a BNF representation of an O/R Address. Hardcastle-Kille [Page 34]
RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992 std-or-address = 1*( "/" attribute "=" value ) "/" attribute = standard-type / "RFC 822" / registered-dd-type / dd-key "." std-printablestring standard-type = key-string registered-dd-type = key-string dd-key = key-string value = std-printablestring std-printablestring = *( std-char / std-pair ) std-char = <"{", "}", "*", and any ps-char except "/" and "="> std-pair = "$" ps-char The standard-type is any key defined in the table in Section 4.2, except PN, and DD. The BNF leads to a set of attribute/value pairs. The value is interpreted according to the EBNF encoding defined in the table. If the standard-type is PN, the value is interpreted according to EBNF.encoded-pn, and the components of MTS.PersonalName and/or MTS.TeletexPersonalName derived accordingly. If dd-key is the recognised Domain Defined string (DD), then the type and value are interpreted according to the syntax implied from the encoding, and aligned to either the teletex or printable string form. Key and value shall have the same encoding. If value is "RFC 822", then the (printable string) Domain Defined Type of "RFC 822" is assumed. This is an optimised encoding of the domain defined type defined by this specification. The matching of all keywords shall be done in a case-independent manner. EBNF.std-or-address uses the characters "/" and "=" as delimiters. Domain Defined Attributes and any value may contain these characters. A quoting mechanism, using the non-printable string "$" is used to allow these characters to be represented. If the value is registered-dd-type, and the value is registered at the Internet Assigned Numbers Authority (IANA) as an accepted Domain Defined Attribute type, then the value shall be interpreted Hardcastle-Kille [Page 35]
RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992 accordingly. This restriction maximises the syntax checking which can be done at a gateway. 4.3. EBNF.822-address <-> MTS.ORAddress Ideally, the mapping specified would be entirely symmetrical and global, to enable addresses to be referred to transparently in the remote system, with the choice of gateway being left to the Message Transfer Service. There are two fundamental reasons why this is not possible: 1. The syntaxes are sufficiently different to make this awkward. 2. In the general case, there would not be the necessary administrative co-operation between the X.400 and RFC 822 worlds, which would be needed for this to work. Therefore, an asymmetrical mapping is defined, which can be symmetrical where there is appropriate administrative control. 4.3.1. X.400 encoded in RFC 822 The std-or-address syntax is used to encode O/R Address information in the 822.local-part of EBNF.822-address. In some cases, further O/R Address information is associated with the 822.domain component. This cannot be used in the general case, due to character set problems, and to the variants of X.400 O/R Addresses which use different attribute types. The only way to encode the full PrintableString character set in a domain is by use of the 822.domain-ref syntax (i.e. 822.atom). This is likely to cause problems on many systems. The effective character set of domains is in practice reduced from the RFC 822 set, by restrictions imposed by domain conventions and policy, and by restrictions in RFC 821. A generic 822.address consists of a 822.local-part and a sequence of 822.domains (e.g., <@domain1,@domain2:user@domain3>). All except the 822.domain associated with the 822.local-part (domain3 in this case) are considered to specify routing within the RFC 822 world, and will not be interpreted by the gateway (although they may have identified the gateway from within the RFC 822 world). The 822.domain associated with the 822.local-part identifies the gateway from within the RFC 822 world. This final 822.domain may be used to determine some number of O/R Address attributes, where this does not conflict with the first role. RFC 822 routing to gateways will usually be set up to facilitate the 822.domain being used for both purposes. The following O/R Address attributes are considered Hardcastle-Kille [Page 36]
RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992 as a hierarchy, and may be specified by the domain. They are (in order of hierarchy): Country, ADMD, PRMD, Organisation, Organisational Unit There may be multiple Organisational Units. A global mapping is defined between domain specifications, and some set of attributes. This association proceeds hierarchically. For example, if a domain implies ADMD, it also implies country. Subdomains under this are associated according to the O/R Address hierarchy. For example: => "AC.UK" might be associated with C="GB", ADMD="GOLD 400", PRMD="UK.AC" then domain "R-D.Salford.AC.UK" maps with C="GB", ADMD="GOLD 400", PRMD="UK.AC", O="Salford", OU="R-D" There are three basic reasons why a domain/attribute mapping might be maintained, as opposed to using simply subdomains: 1. As a shorthand to avoid redundant X.400 information. In particular, there will often be only one ADMD per country, and so it does not need to be given explicitly. 2. To deal with cases where attribute values do not fit the syntax: domain-syntax = alphanum [ *alphanumhyphen alphanum ] alphanum = <ALPHA or DIGIT> alphanumhyphen = <ALPHA or DIGIT or HYPHEN> Although RFC 822 allows for a more general syntax, this restricted syntax is chosen as it is the one chosen by the various domain service administrations. 3. To deal with missing elements in the hierarchy. A domain may be associated with an omitted attribute in conjunction with several present ones. When performing the algorithmic insertion of components lower in the hierarchy, the omitted value shall be skipped. For example, if "HNE.EGM" is associated with "C=TC", "ADMD=ECQ", "PRMD=HNE", and omitted organisation, then "ZI.HNE.EGM" is mapped with "C=TC", "ADMD=ECQ", "PRMD=HNE", "OU=ZI". Attributes may have null values, and this is treated separately from omitted attributes (whilst it would be bad practice to treat these Hardcastle-Kille [Page 37]
RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992 two cases differently, they must be allowed for). This set of mappings needs be known by the gateways relaying between the RFC 822 world, and the O/R Address space associated with the mapping in question. There needs to be a single global definition of this set of mappings. A mapping implies an adminstrative equivalence between the two parts of the namespaces which are mapped together. To correctly route in all cases, it is necessary for all gateways to know the mapping. To facilitate distribution of a global set of mappings, a format for the exchange of this information is defined in Appendix F. The remaining attributes are encoded on the LHS, using the EBNF.std- or-address syntax. For example: /I=J/S=Linnimouth/GQ=5/@Marketing.Widget.COM encodes the MTS.ORAddress consisting of: MTS.CountryName = "TC" MTS.AdministrationDomainName = "BTT" MTS.OrganizationName = "Widget" MTS.OrganizationalUnitNames.value = "Marketing" MTS.PersonalName.surname = "Linnimouth" MTS.PersonalName.initials = "J" MTS.PersonalName.generation-qualifier = "5" The first three attributes are determined by the domain Widget.COM. Then, the first element of OrganizationalUnitNames is determined systematically, and the remaining attributes are encoded on the LHS. In an extreme case, all of the attributes will be on the LHS. As the domain cannot be null, the RHS will simply be a domain indicating the gateway. The RHS (domain) encoding is designed to deal cleanly with common addresses, and so the amount of information on the RHS is maximised. In particular, it covers the Mnemonic O/R Address using a 1984 compatible encoding. This is seen as the dominant form of O/R Address. Use of other forms of O/R Address, and teletex encoded attributes will require an LHS encoding. There is a further mechanism to simplify the encoding of common cases, where the only attributes to be encoded on the LHS is a (non- Teletex) Personal Name attributes which comply with the restrictions of 4.2.1. To achieve this, the 822.local-part shall be encoded as EBNF.encoded-pn. In the previous example, if the GenerationQualifier was not present in the previous example O/R Address, it would map with the RFC 822 address: J.Linnimouth@Marketing.Widget.COM. Hardcastle-Kille [Page 38]
RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992 From the standpoint of the RFC 822 Message Transfer System, the domain specification is simply used to route the message in the standard manner. The standard domain mechanisms are used to select appropriate gateways for the corresponding O/R Address space. In most cases, this will be done by registering the higher levels, and assuming that the gateway can handle the lower levels. 4.3.2. RFC 822 encoded in X.400 In some cases, the encoding defined above may be reversed, to give a "natural" encoding of genuine RFC 822 addresses. This depends largely on the allocation of appropriate management domains. The general case is mapped by use of domain defined attributes. A Domain defined type "RFC 822" is defined. The associated attribute value is an ASCII string encoded according to Section 3.3.3 of this specification. The interpretation of the ASCII string depends on the context of the gateway. 1. In the context of RFC 822, and RFC 920 [Crocker82a,Postel84a], the string can be used directly. 2. In the context of the JNT Mail protocol, and the NRS [Kille84a,Larmouth83a], the string shall be interpreted according to Mailgroup Note 15 [Kille84b]. 3. In the context of UUCP based systems, the string shall be interpreted as defined in [Horton86a]. Other O/R Address attributes will be used to identify a context in which the O/R Address will be interpreted. This might be a Management Domain, or some part of a Management Domain which identifies a gateway MTA. For example: C = "GB" ADMD = "GOLD 400" PRMD = "UK.AC" O = "UCL" OU = "CS" "RFC 822" = "Jimmy(a)WIDGET-LABS.CO.UK" OR C = "TC" ADMD = "Wizz.mail" PRMD = "42" "rfc-822" = "postel(a)venera.isi.edu" Hardcastle-Kille [Page 39]
RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992
RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992 MTA.ReportTransferEnvelope.internal-trace-information Mapped onto the extended RFC 822 field "X400-Received:", as described in Section 5.3.7. The first element is also used to generate the "Date:" field, and the EBNF.report-point. MTA.PerRecipientReportTransferFields.last-trace-information Mapped to EBNF.recipient-info (last trace) MTA.PerReportTransferFields.subject-intermediate-trace- information Mapped to EBNF.drc-field (Subject-Intermediate- Trace-Information). These fields are ordered so that the most recent trace element comes first. Example Delivery Reports Example Delivery Report 1: Return-Path: <postmaster@cs.ucl.ac.uk> Received: from cs.ucl.ac.uk by bells.cs.ucl.ac.uk via Delivery Reports Channel id <27699-0@bells.cs.ucl.ac.uk>; Thu, 7 Feb 1991 15:48:39 +0000 From: UCL-CS MTA <postmaster@cs.ucl.ac.uk> To: S.Kille@cs.ucl.ac.uk Subject: Delivery Report (failure) for H.Hildegard@bbn.com Message-Type: Delivery Report Date: Thu, 7 Feb 1991 15:48:39 +0000 Message-ID: <"bells.cs.u.694:"@cs.ucl.ac.uk> Content-Identifier: Greetings. ------------------------------ Start of body part 1 This report relates to your message: Greetings. of Thu, 7 Feb 1991 15:48:20 +0000 Your message was not delivered to H.Hildegard@bbn.com for the following reason: Bad Address MTA 'bbn.com' gives error message (USER) Unknown user name in "H.Hildegard@bbn.com" ***** The following information is directed towards the local ***** administrator and is not intended for the end user * * DR generated by mta bells.cs.ucl.ac.uk * in /PRMD=uk.ac/ADMD=gold 400/C=gb/ * at Thu, 7 Feb 1991 15:48:34 +0000 Hardcastle-Kille [Page 88]
RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992 * * Converted to RFC 822 at bells.cs.ucl.ac.uk * at Thu, 7 Feb 1991 15:48:40 +0000 * ..... continued on next page * Delivery Report Contents: * * Subject-Submission-Identifier: * [/PRMD=uk.ac/ADMD=gold 400/C=gb/;<1803.665941698@UK.AC.UCL.CS>] * Content-Identifier: Greetings. * Subject-Intermediate-Trace-Information: /PRMD=uk.ac/ADMD=gold 400/C=gb/; * arrival Thu, 7 Feb 1991 15:48:20 +0000 action Relayed * Subject-Intermediate-Trace-Information: /PRMD=uk.ac/ADMD=gold 400/C=gb/; * arrival Thu, 7 Feb 1991 15:48:18 +0000 action Relayed * Recipient-Info: H.Hildegard@bbn.com, * /RFC 822=H.Hildegard(a)bbn.com/OU=cs/O=ucl /PRMD=uk.ac/ADMD=gold 400/C=gb/; * FAILURE reason Unable-To-Transfer (1); * diagnostic Unrecognised-ORName (0); * last trace (ia5) Thu, 7 Feb 1991 15:48:18 +0000; * supplementary info "MTA 'bbn.com' gives error message (USER) * Unknown user name in "H.Hildegard@bbn.com""; ****** End of administration information The Original Message follows: ------------------------------ Start of forwarded message 1 Received: from glenlivet.cs.ucl.ac.uk by bells.cs.ucl.ac.uk with SMTP inbound id <27689-0@bells.cs.ucl.ac.uk>; Thu, 7 Feb 1991 15:48:21 +0000 To: H.Hildegard@bbn.com Subject: Greetings. Phone: +44-71-380-7294 Date: Thu, 07 Feb 91 15:48:18 +0000 Message-ID: <1803.665941698@UK.AC.UCL.CS> From: Steve Kille <S.Kille@cs.ucl.ac.uk> Steve ------------------------------ End of forwarded message 1 Example Delivery Report 2: Hardcastle-Kille [Page 89]
RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992 Return-Path: <postmaster@cs.ucl.ac.uk> Received: from cs.ucl.ac.uk by bells.cs.ucl.ac.uk via Delivery Reports Channel id <27718-0@bells.cs.ucl.ac.uk>; Thu, 7 Feb 1991 15:49:11 +0000 X400-Received: by mta bells.cs.ucl.ac.uk in /PRMD=uk.ac/ADMD=gold 400/C=gb/; Relayed; Thu, 7 Feb 1991 15:49:08 +0000 X400-Received: by /PRMD=DGC/ADMD=GOLD 400/C=GB/; Relayed; Thu, 7 Feb 1991 15:48:40 +0000 From: UCL-CS MTA <postmaster@cs.ucl.ac.uk> To: S.Kille@cs.ucl.ac.uk Subject: Delivery Report (failure) for j.nosuchuser@dle.cambridge.DGC.gold-400.gb Message-Type: Delivery Report Date: Thu, 7 Feb 1991 15:49:11 +0000 Message-ID: <"DLE/910207154840Z/000"@cs.ucl.ac.uk> Content-Identifier: A useful mess... This report relates to your message: A useful mess... Your message was not delivered to j.nosuchuser@dle.cambridge.DGC.gold-400.gb for the following reason: Bad Address DG 21187: (CEO POA) Unknown addressee. ***** The following information is directed towards the local ***** administrator and is not intended for the end user * * DR generated by /PRMD=DGC/ADMD=GOLD 400/C=GB/ * at Thu, 7 Feb 1991 15:48:40 +0000 * * Converted to RFC 822 at bells.cs.ucl.ac.uk * at Thu, 7 Feb 1991 15:49:12 +0000 * * Delivery Report Contents: * * Subject-Submission-Identifier: * [/PRMD=uk.ac/ADMD=gold 400/C=gb/;<1796.665941626@UK.AC.UCL.CS>] * Content-Identifier: A useful mess... * Recipient-Info: j.nosuchuser@dle.cambridge.DGC.gold-400.gb, * /I=j/S=nosuchuser/OU=dle/O=cambridge/PRMD=DGC/ADMD=GOLD 400/C=GB/; * FAILURE reason Unable-To-Transfer (1); * diagnostic Unrecognised-ORName (0); * supplementary info "DG 21187: (CEO POA) Unknown addressee."; ****** End of administration information The Original Message is not available Hardcastle-Kille [Page 90]
RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992 5.3.9. Probe This is an MTS internal issue. Any probe shall be serviced by the gateway, as there is no equivalent RFC 822 functionality. The value of the reply is dependent on whether the gateway could service an MTS Message with the values specified in the probe. The reply shall make use of MTS.SupplementaryInformation to indicate that the probe was serviced by the gateway. Appendix A - Mappings Specific to SMTP This Appendix is specific to the Simple Mail Transfer Protocol (RFC 821). It describes specific changes in the context of this protocol. When servicing a probe, as described in section 5.3.9, use may be made of the SMTP VRFY command to increase the accuracy of information contained in the delivery report. Appendix B - Mappings specific to the JNT Mail This Appendix is specific to the JNT Mail Protocol. It describes specific changes in the context of this protocol. 1. Introduction There are five aspects of a gateway which are JNT Mail Specific. These are each given a section of this appendix. 2. Domain Ordering When interpreting and generating domains, the UK NRS domain ordering shall be used, both in headers, and in text generated for human description. 3. Addressing A gateway which maps to JNT Mail should recognise the Domain Defined Attribute JNT-MAIL. The value associated with this attribute should be interpreted according to the JNT Mail Specification. This DDA shall never be generated by a gateway. For this reason, the overflow mechanism is not required. 4. Acknowledge-To: This field has no direct functional equivalent in X.400. However, it can be supported to an extent, and can be used to improve X.400 support. If an Acknowledge-To: field is present when going from JNT Mail to Hardcastle-Kille [Page 91]
RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992 X.400, there are two different situations. The first case is where there is one address in the Acknowledge-To: field, and it is equal to the 822-MTS return address. In this case, the MTS.PerRecipientSubmissionFields.originator-request-report.report shall be set for each recipient, and the Acknowledge-To: field discarded. Here, X.400 can provide the equivalent service. In all other cases two actions are taken. 1. Acknowledgement(s) may be generated by the gateway. The text of these acknowledgements shall indicate that they are generated by the gateway, and do not correspond to delivery. 2. The Acknowledge-To: field shall be passed as an extension heading. When going from X.400 to JNT Mail, in cases where MTA.PerRecipientMessageTransferFields.per-recipient-indicators. originator-report bit is set for all recipients (i.e., there is a user request for a positive delivery report for every recipeint), generate an Acknowledge-To: field containing the MTS.OtherMessageDeliveryFields.originator-name. Receipt notification requests are not mapped onto Acknowledge-To:, as no association can be guaranteed between IPMS and MTS level addressing information. 5. Trace JNT Mail trace uses the Via: syntax. When going from JNT Mail to X.400, a mapping similar to that for Received: is used. No MTS.GlobalDomainIdentifier of the site making the trace can be derived from the Via:, so a value for the gateway is used. The trace text, including the "Via:", is unfolded, truncated to MTS.ub-mta-name-length (32), and mapped to MTA.InternalTraceInformationElement.mta-name. There is no JNT Mail specific mapping for the reverse direction. 6. Timezone specification The extended syntax of zone defined in the JNT Mail Protocol shall be used in the mapping of UTCTime defined in Chapter 3. 7. Lack of 822-MTS originator specification In JNT Mail the default mapping of the MTS.OtherMessageDeliveryFields.originator-name is to the Sender: field. This can cause a problem when going from X.400 to JNT Mail if the mapping of IPMS.Heading has already generated a Sender: Hardcastle-Kille [Page 92]
RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992
RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992 - Which 822-MTS protocols are supported. The relevant appendices must be followed to claim support of a given protocol: SMTP (A); JNT Mail (B); UUCP (C). - Which X.400 versions are supported (84 and/or 88). - The means by which it can access the global mappings. Currently, the tables of the formats define in Appendix F is the only means available. - The approach taken when upper bounds are exceeded at the IPM level (5.1.3) - The approach taken to return of contents (5.2) - The approach taken to body parts which cannot be converted (5.3.4) - The approach taken to multiple copies vs non-disclosure ( The following are optional parts of this specification. A conforming implementation should specify which of these it supports. - Generation of extended RFC 822 fields is mandatory. Optionally, they may be parsed and mapped back to X.400. A gateway should should indicate if this is done. - Support for the extension mappings of Appendix H. - Support for returning illegal format content in a delivery report - Which address interpretation heuristics are supported ( - If RFC 987 generated message ids are handled in a backwards compatible manner ( Appendix J - Change History: RFC 987, 1026, 1138, 1148 RFC 987 was the original document, and contained the key elements of this specification. It was specific to X.400(1984). RFC 1026 specified a small number of necessary changes to RFC 987. RFC 1138 was based on the RFC 987 work. It contained an editorial error, and was reissued a few months later as RFC 1148. RFC 1148 will be referred to here, as it is the document which is widely Hardcastle-Kille [Page 107]
RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992 referred to elsewhere. The major goal of RFC 1148 was to upgrade RFC 987 to X.400(1988). It did this, but did not obsolete RFC 987, which was recommended for use with X.400(1984). This appendix summarises the changes made in going from RFC 987 to RFC 1148. RFC 1148 noted the following about its upgrade from RFC 987: Unnecessary change is usually a bad idea. Changes on the RFC 822 side are avoided as far as possible, so that RFC 822 users do not see arbitrary differences between systems conforming to this specification, and those following RFC 987. Changes on the X.400 side are minimised, but are more acceptable, due to the mapping onto a new set of services and protocols. 1. Introduction The model has shifted from a protocol based mapping to a service based mapping. This has increased the generality of the specification, and improved the model. This change affects the entire document. A restriction on scope has been added. 2. Service Elements - The new service elements of X.400 are dealt with. - A clear distinction is made between origination and reception 3. Basic Mappings - Add teletex support - Add object identifier support - Add labelled integer support - Make PrintableString <-> ASCII mapping reversible - The printable string mapping is aligned to the NBS mapping derived from RFC 987. 4. Addressing - Support for new addressing attributes - The message ID mapping is changed to not be table driven Hardcastle-Kille [Page 108]
RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992 5. Detailed Mappings - Define extended IPM Header, and use instead of second body part for RFC 822 extensions - Realignment of element names - New syntax for reports, simplifying the header and introducing a mandatory body format (the RFC 987 header format was unusable) - Drop complex autoforwarded mapping - Add full mapping for IP Notifications, defining a body format - Adopt an MTS Identifier syntax in line with the O/R Address syntax - A new format for X400 Trace representation on the RFC 822 side 6. Appendices - Move Appendix on restricted 822 mappings to a separate RFC - Delete Phonenet and SMTP Appendixes Appendix K - Change History: RFC 1148 to this Document 1. General - The scope of the document was changed to cover X.400(1984), and so obsolete RFC 987. - Changes were made to allow usage to connect RFC 822 networks using X.400 - Text was tightened to be clear about optional and mandatory aspects - A good deal of clarification - A number of minor EBNF errors - Better examples are given - Further X.400 upper bounds are handled correctly Hardcastle-Kille [Page 109]
RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992 2. Basic Mappings - The encoding of object identifier is changed slightly 3. Addressing - A global mapping of domain to preferred gateway is introduced. - An overflow mechanism is defined for RFC 822 addresses of greater than 128 bytes. - Changes were made to improve compatability with the PDAM on writing O/R Addresses. + The PD and Terminal Type keywords were aligned to the PDAM. It is believed that minimal use has been made of the RFC 1148 keywords. + P and A are allowed as alternate keys for PRMD and ADMD + Where keywords are different, the PDAM keywords are alternatives on input. This is mandatory. 4. Detailed Mappings - The format of the Subject: lines is defined. - Illegal use (repetition) of the heading EXTENSION is corrected, and a new object identifier assigned. - The Delivery Report format is extensively revised in light of operational experience. - The handling of redirects is significantly changed, as the previous mechanism did not work. 5. Appendices - An SMTP appendix is added, allowing optional use of the VRFY command to improve probe information. - Handling of JNT Mail Acknowledge-To is changed slightly. - A DDA JNT-MAIL is allowed on input. - The format definitions of Appendix F are explained further, and a third table definition added. Hardcastle-Kille [Page 110]
RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992 - An appendix on use with X.400(1984) is added. - Optional extensions are defined to give RFC 822 access to further X.400 facilities. - An appendix on conformance is added. References CCITT88a. CCITT, "CCITT Recommendations X.408," Message Handling Systems: Encoded Information Type Conversion Rules, December 1988 CCITT/ISO88a. CCITT/ISO, "CCITT Recommendations X.400/ ISO IS 10021-1," Message Handling: System and Service Overview , December 1988 CCITT/ISO88b. CCITT/ISO, "CCITT Recommendations X.420/ ISO IS 10021-7," Message Handling Systems: Interpersonal Messaging System, December 1988. CCITT/ISO88c. CCITT/ISO, "CCITT Recommendations X.411/ ISO IS 10021-4," Message Handling Systems: Message Transfer System: Abstract Service Definition and Procedures, December 1988. CCITT/ISO88d. CCITT/ISO, "Specification of Abstract Syntax Notation One (ASN.1)," CCITT Recommendation X.208 / ISO IS 8824, December 1988 CCITT/ISO91a. CCITT/ISO, "Representation of O/R Addresses for Human Usage," PDAM to CCITT X.401 / ISO/IEC 10021-2, February 1991 Crocker82a. Crocker, D., "Standard of the Format of ARPA Internet Text Messages," RFC 822, UDEL, August 1982. Hardcastle-K92. Hardcastle-Kille, S., "X.400 1988 to 1984 downgrading," RFC 1328, UCL, May 1992. Hardcastle-Kille [Page 111]
RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992 Horton86a. Horton, M., "UUCP Mail Interchange Format Standard," RFC 976, February 1986. Kille84b. Kille, S., "Gatewaying between RFC 822 and JNT Mail," JNT Mailgroup Note 15, May 1984. Kille84a. Kille, S., (Editor), JNT Mail Protocol (revision 1.0), Joint Network Team, Rutherford Appleton Laboratory, March 1984. Kille86a. Kille, S., "Mapping Between X.400 and RFC 822," UK Academic Community Report (MG.19) / RFC 987, June 1986. Kille87a. Kille, S., "Addendum to RFC 987," UK Academic Community Report (MG.23) / RFC 1026, August 1987. Kille89a. Kille, S., "A String Encoding of Presentation Address," UCL Research Note 89/14, March 1989. Kille89b. Kille, S., "Mapping between full RFC 822 and RFC 822 with restricted encoding," RFC 1137, October 1989. Kille90a. Kille, S., "Mapping Between X.400(1988) / ISO 10021 and RFC 822," RFC 1148, March 1990. Larmouth83a. Larmouth, J., "JNT Name Registration Technical Guide," Salford University Computer Centre, April 1983. Postel84a. Postel J., and J. Reynolds, "Domain Requirements," RFC 920, USC/Information Sciences Institute, October 1984. Postel82a. Postel, J., "Simple Mail Transfer Protocol", RFC 821, USC/Information Sciences Institute, August 1982. Rose85a. Rose M., and E. Stefferud, "Proposed Standard for Message Encapsulation," RFC 934, January 1985. Hardcastle-Kille [Page 112]
RFC 1327 Mapping between X.400(1988) and RFC 822 May 1992 Systems85a. CEN/CENELEC/Information Technology/Working Group on Private Message Handling Systems, "FUNCTIONAL STANDARD A/3222," CEN/CLC/IT/WG/PMHS N 17, October 1985.

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