Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!csd4.milw.wisc.edu!cs.utexas.edu!uunet!ncis.tis.llnl.gov!CS.UCL.AC.UK!S.Kille From: S.Kille@CS.UCL.AC.UK (Steve Kille) Newsgroups: comp.protocols.iso.x400.gateway Subject: Fw: 1 of 5 Message-ID: <1032.616429221@UK.AC.UCL.CS> Date: 14 Jul 89 14:20:21 GMT Sender: root@ncis.tis.llnl.gov Reply-To: kehres@tis.llnl.gov Distribution: inet Organization: The Internet Lines: 1380 Approved: post-x400-gateway@tis.llnl.gov | Mailgroup Note nnn UCL Research Note nnn Network Working Group S.E. Kille Request for Comments 987(88) University College London 16th July 1989 Mapping between X.400(1988) / ISO 10021 and RFC | 822 Status of this Memo: EDITOR'S NOTE: THIS IS DRAFT VERSION 2.0. THE INTERIM NUMBER 987(88) WILL BE REPLACED WHEN THIS DOCUMENT IS FINALISED. This RFC suggests a proposed protocol mapping for the ARPA- Internet community and UK Academic Community, and requests discussion and suggestions for improvements. Distribution of this memo is unlimited. This document describes a set of mappings which will enable interworking between systems operating the CCITT X.400 (1988) Recommendations on Message Handling Systems / ISO IEC 10021 Message Oriented Text Interchange Systems (MOTIS) [CCITT/ISO88a], and systems using the RFC 822 mail protocol[Crocker82a] or protocols derived from RFC 822. The approach aims to maximise the services offered across the boundary, whilst not requiring unduly complex mappings. The mappings should not require any changes to end systems. This document is based on RFC 987 and RFC 1026 [Kille86a,Kille87a], which define a similar mapping for Kille [page 1] RFC 987(88) Mapping between X.400(1988) and RFC 822 DRAFT Version 2.0 X.400 (1984). This document does not obsolete the earlier ones, as its domain of application is different. Specification: This document specifies a mapping between two protocols. This specification should be used when this mapping is performed on the 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. * Kille [page 2] RFC 987(88) Mapping between X.400(1988) and RFC 822 DRAFT Version 2.0 Table of Contents 1 - Overview ...................................... 6 1.1 - X.400 ......................................... 6 1.2 - RFC 822 ....................................... 6 1.3 - The need for conversion ....................... 7 1.4 - General approach .............................. 8 1.5 - Gatewaying Model .............................. 8 1.6 - RFC 987 ....................................... 11 1.7 - Aspects not covered ........................... 12 1.8 - Subsetting .................................... 12 1.9 - Document Structure ............................ 13 1.10 - Acknowledgements ............................. 14 2 - Service Elements .............................. 15 2.1 - The Notion of Service Across a Gateway .....15. | 2.2 - .mc ........................................... 16 2.3 - X.400 ......................................... 20 3 - Basic Mappings ................................ 31 3.1 - Notation ...................................... 31 3.2 - ASCII and IA5 ................................. 32 Kille [page 3] RFC 987(88) Mapping between X.400(1988) and RFC 822 DRAFT Version 2.0 3.3 - .mc | .....32.................................. | 3.4 - Encoding ASCII in Printable String ............ 35 4 - Addressing .................................... 37 4.1 - A textual representation of MTS.ORAddress ..... 37 4.2 - Basic Representation .......................... 37 4.3 - EBNF.822-address <-> MTS.ORAddress ............ 43 4.4 - Repeated Mappings ............................. 53 4.5 - Directory Names ............................... 54 4.6 - MTS Mappings .................................. 55 4.7 - IPMS Mappings ................................. 58 5 - Detailed Mappings ............................. 64 5.1 - RFC 822 -> X.400 .............................. 64 5.2 - Return of Contents ............................ 71 5.3 - X.400 -> RFC 822 .............................. 72 Appendix A - Quoted String Encodings ....................... 95 1 - Introduction .................................. 95 2 - ASCII <-> 822.atom ............................ 95 3 - 822.local-part <-> ASCII ...................... 96 Appendix B - Mappings specific to the JNT Mail ............. 98 1 - Introduction .................................. 98 2 - Domain Ordering ............................... 98 3 - Acknowledge-To: .............................. 98 Kille [page 4] RFC 987(88) Mapping between X.400(1988) and RFC 822 DRAFT Version 2.0 4 - Trace ......................................... 99 5 - Timezone specification ........................ 99 6 - Lack of 822-MTS originator specification ...... 99 Appendix C - Mappings specific to UUCP Mail .....101........ | Appendix D - Object Identifier Assignment .....102.......... | Appendix E - BNF Summary .....103........................... | Appendix F - Format of address mapping tables .....112...... | Appendix G - Differences with RFC 987 .....114.............. | 1 - Introduction .................................. 114 2 - Service Elements .............................. 114 3 - Basic Mappings ................................ 114 4 - Addressing .................................... 114 5 - Detailed Mappings ............................. 115 6 - Appendices .....115............................ | Kille [page 5] 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 applications 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 are likely to use domains which conform to RFC 920, but not the corresponding domain nameservers [Horton86a]. Kille [page 6] RFC 987(88) Mapping between X.400(1988) and RFC 822 DRAFT Version 2.0 Csnet Some portions of Csnet will follow the DARPA Internet protocols. The dialup portion of Csnet uses the Phonenet protocols as a replacement for RFC 821. This portion uses domains which conform to RFC 920, but not the corresponding domain nameservers. 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 be a requirement, even in cases where communities intend to make a transition to use of an X.400 IPMS, where 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 which 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. Kille [page 7] RFC 987(88) Mapping between X.400(1988) and RFC 822 DRAFT Version 2.0 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. 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/IS 10021-7 [CCITT/ISO88b], which comprises of three basic services: | 1. Origination 2. Reception 3. Management Kille [page 8] RFC 987(88) Mapping between X.400(1988) and RFC 822 DRAFT Version 2.0 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 define the interaction between MTAs, along with the procedures for distributed operation. This service provides Kille [page 9] RFC 987(88) Mapping between X.400(1988) and RFC 822 DRAFT Version 2.0 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 proposed. 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 Kille [page 10] RFC 987(88) Mapping between X.400(1988) and RFC 822 DRAFT Version 2.0 IPMS Services). Going from X.400 to RFC 822, an RFC 822 message and the associated 822-MTS information may be derived from: 1. A Report (MTA, and MTS Services) | 2. An IPN (MTA, MTS, and IPMS services) 3. An IPM (MTA, MTS, and IPMS services) Probes (MTA Service) must be processed by the gateway, as discussed in Chapter 5. MTS Messages containing Content Types | other than those defined by the IPMS are not mapped by the gateway, and should be rejected at the gateway. 1.5.4. Repeated Mappings The mappings specified here are designed to work where a message traverses multiple times between X.400 and RFC 822. This is often essential, particularly in the case of distribution lists. However, in general, this will lead to a level of service which is the lowest common denominator (approximately the services | offered by RFC 822). In particular, there is no expectation of additional X.400 services being mapped - although this may be possible in some cases. 1.6. RFC 987 Much of this work is based on the initial specification of RFC 987 and in its addendum RFC 1026. A basic decision is that the mapping will be to the full 1988 version of X.400, and not to a 1984 compatible subset. This is important, to give good support to communities which will utilise full X.400 at an early date. This has the following implications: - This document does not obsolete RFC 987, as it has a different domain of application. - If a gatewayed message is being transferred to a 1984 | system, then RFC 987 should be used. If the X.400 side of the gateway is a 1988 system, then it should be operated in 1984 compatibility mode. There is no advantage and some disadvantage in using the new mapping, and later on applying X.400 downgrading rules. Note that in an environment where | RFC 822 is of major importance, it may be desirable for | Kille [page 11] RFC 987(88) Mapping between X.400(1988) and RFC 822 DRAFT Version 2.0 downgrading to consider the case where the message was | originated in an RFC 822 system, and mapped according to | this specification. - New features of X.400 can be used to provide a much cleaner | mapping than that defined in RFC 987. Unnecessary change is usually a bad idea. Changes on the RFC 822 side are avoided as far as possible, so that RFC 822 users do not see arbitrary differences between systems conforming to this specification, and those following RFC 987. Changes on the X.400 side are minimised, but are more acceptable, due to the mapping onto a new set of services and protocols. A summary of changes made is given in Appendix I. 1.7. Aspects not covered There have been a number of cases where RFC 987 was used in a | manner which was not intended. This section is to make clear some limitations of scope. In particular, this specification | does not specify: - Extensions of RFC 822 to provide access to all X.400 services - X.400 user interface definition These are really coupled. To map the X.400 services, this specification defines a number of extensions to RFC 822. As a side effect, these give the 822 user access to SOME X.400 services. However, the aim on the RFC 822 side is to preserve current service, and it is intentional that access is not given to all X.400 services. Thus, it will be a poor choice for X.400 | implementors to use 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. 1.8. Subsetting This proposal specifies a mapping which is appropriate to preserve services in existing RFC 822 communities. Implementations and specifications which subset this Kille [page 12] RFC 987(88) Mapping between X.400(1988) and RFC 822 DRAFT Version 2.0 specification are strongly discouraged. 1.9. Document Structure This document has five chapters: 1. Overview - this chapter. 2. Service Elements - This describes the (end user) services mapped by a gateway. 3. Basic mappings - This describes some basic notation used in Chapters 3-5, the mappings between character sets, and some fundamental protocol elements. 4. Addressing - This considers the mapping between X.400 O/R names and RFC 822 addresses, which is a fundamental gateway component. 5. Detailed Mappings - This describes the details of all other mappings. There are also seven appendices: | A. Quoted String Encodings B. Mappings Specific to JNT Mail C. Mappings Specific to UUCP Mail | D. Object Identifier Assignment | E. BNF Summary F. Format of Address Tables G. Differences with RFC 987 | 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 | Kille [page 13] RFC 987(88) Mapping between X.400(1988) and RFC 822 DRAFT Version 2.0 YOU ARE FAMILIAR WITH THESE SPECIFICATIONS. 1.10. Acknowledgements This work was partly sponsored by the Joint Network Team. The | workshop at UCL in June 1989 to work on this specification was | also an IFIP WG 6.5 meeting. | The work in this specification was substantially based on | RFC 987, which had input from many people. | Useful comments and suggestions were made by Jim Craigie | (JNT), Christian Huitema (Inria), Peter Lynch (Prime), Julian | Onions (Nottingham Univ), Sandy Shaw (Edinburgh Univ), Einar | Stefferud (NMA), and Peter Sylvester (GMD). Kille [page 14] RFC 987(88) Mapping between X.400(1988) and RFC 822 DRAFT Version 2.0 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 is 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. 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. | There are three cases. | Supported | The corresponding protocol elements map well, and so the service can be fully provided. | Kille [page 15] RFC 987(88) Mapping between X.400(1988) and RFC 822 DRAFT Version 2.0 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. 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 | Kille [page 16] RFC 987(88) Mapping between X.400(1988) and RFC 822 DRAFT Version 2.0 822 header into a heading extension in the IPM (InterPersonal | Message). This can be regarded as partial support, as it makes the information available to any X.400 implementations which are interested in these services. Communities which require significant RFC 822 interworking should require that their X.400 | User Agents are able to display these heading extensions. Support for the various service elements (headers) is now listed. Date: Supported. From: Supported. For messages where there is also a sender field, the mapping is to "Authorising Users Indication", which has | subtly different semantics to the general RFC 822 usage of From:. Sender: Supported. Reply-To: Supported. To: Supported. Cc: Supported. Bcc: Supported. Message-Id: Supported. In-Reply-To: Supported, for a single reference. Where multiple | references are given, partial support is given by mapping to | "Cross Referencing Indication". This gives similar | semantics. References: Supported. | Keywords: Supported by use of a heading extension. | Kille [page 17] RFC 987(88) Mapping between X.400(1988) and RFC 822 DRAFT Version 2.0 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: Kille [page 18] RFC 987(88) Mapping between X.400(1988) and RFC 822 DRAFT Version 2.0 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: | 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: Kille [page 19] RFC 987(88) Mapping between X.400(1988) and RFC 822 DRAFT Version 2.0 Priority: * Redirection-History: Reply-By: 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. | Kille [page 20] RFC 987(88) Mapping between X.400(1988) and RFC 822 DRAFT Version 2.0 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. These services are listed in the order | given in X.400. 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 | Kille [page 21] RFC 987(88) Mapping between X.400(1988) and RFC 822 DRAFT Version 2.0 (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. These services | are listed in the order given in X.400. 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. | Kille [page 22] RFC 987(88) Mapping between X.400(1988) and RFC 822 DRAFT Version 2.0 This service really means giving the user control as to | whether or not an alternate recipient is allowed. This | specification always transfers a message, 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). | Kille [page 23] RFC 987(88) Mapping between X.400(1988) and RFC 822 DRAFT Version 2.0 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, |