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RFC 0987

Mapping between X.400 and RFC 822

Pages: 69
Obsoleted by:  21561327
Updated by:  102611381148
Part 2 of 2 – Pages 32 to 69
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ToP   noToC   RFC0987 - Page 32   prevText
                 "UUCP") appropriate to the gateway should be selected,
                 and its value set.

            3.   Build the rest of the O/R Name in the local Management
                 Domain agreed manner, so that the O/R Name will receive
                 a correct global interpretation.

      4.2.4.  X.400 -> RFC 822

         There are two basic cases:

            1.   RFC 822 addresses encoded in X.400.

            2.   "Genuine" X.400 addresses.  This may include
                 symmetrically encoded RFC 822 addresses.

         When a P1 Recipient O/R Name is interpreted, gatewaying will be
         selected if there a single special domain defined attribute
         present ("RFC-822", "JNT-Mail" or "UUCP").  In this case, use
         mapping A.  For other O/R Names which

            1.   Contain the special attribute.


            2.   Identify the local gateway with the other attributes.

         Use mapping A.  In other cases, use mapping B.

         Mapping A

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

            2.   Where appropriate (P1 recipients), interpret the string
                 according to the semantics implied by the domain
                 defined attribute.

         Mapping B.

         This will be used for X.400 addresses which do not use the
         explicit RFC 822 encoding.

            1.   Noting the hierarchy specified in 4.3.1, determine the
                 maximum set of attributes which have an associated
                 domain specification. If no match is found, allocate
ToP   noToC   RFC0987 - Page 33
                 the domain as the domain specification of the local
                 gateway, and go to step 4.

            2.   Following the 4.3.1 hierarchy, if each successive
                 component exists, and conforms to the syntax
                 EBNF.domain-syntax (as defined in 4.3.1), allocate the
                 next subdomain.

            3.   If the remaining components are personal-name
                 components, conforming to the restrictions of 4.2.2,
                 then EBNF.encoded-pn should be derived to form
                 822.local-part.  In other cases the remaining
                 components should simply be encoded as a 822.local-part
                 using the EBNF.std-orname syntax.  Where registered
                 domain defined types exist, the DD. syntax should not
                 be used.

            4.   If this step is reached for an 822-P1 recipient, then
                 the address is invalid.  For other addresses, if the
                 derived 822.local-part can only be encoded by use of
                 822.quoted-string, the gateway may optionally use the
                 ASCII to 822.local-part mapping defined in Appendix A,
                 dependent on the mail protocols of the networks being
                 relayed to.  Use of this encoding is discouraged.

   4.3.  Repeated Mappings

      The mappings defined are symmetrical across a single gateway,
      except in certain pathological cases (see chapter 3).  However, it
      is always possible to specify any valid address across a gateway.
      This symmetry is particularly useful in cases of (mail exploder
      type) distribution list expansion.  For example, an X.400 user
      sends to a list on an RFC 822 system which he belongs to.  The
      received message will have the originator and any 3rd party X.400
      O/R names in correct format (rather than doubly encoded).  In
      cases (X.400 or RFC 822) where there is common agreement on
      gateway identification, then this will apply to multiple gateways.

      However, the syntax may be used to source route.

      For example:  X.400 -> RFC 822  -> X.400

         C               = "UK"
         ADMD            = "BT"
         PRMD            = "AC"
         "JNT-Mail"      = "/PN=Duval/DD.Title=Manager/(a)FR.PTT.Inria"
ToP   noToC   RFC0987 - Page 34
         This will be sent to an arbitrary UK Academic Community gateway
         by X.400.  Then by JNT Mail to another gateway determined by
         the domain FR.PTT.Inria.  This will then derive the X.400 O/R

            C               = "FR"
            ADMD            = "PTT"
            PRMD            = "Inria"
            PN.S            = "Duval"
            "Title"         = "Manager"

      Similarly:  RFC 822 -> X.400 -> RFC 822



         The second case uses the Appendix A encoding to avoid
         822.quoted-text. This will be sent to by
         RFC 822, then to the AC PRMD by X.400, and then to by RFC 822.

   4.4.  The full P1 / 822-P1 mapping

      There are two basic mappings at the P1 level:

         1.   822-P1 return address <-> P1.UMPDUEnvelope.originator

         2.   822-P1 recipient <-> P1.RecipientInfo

      822-P1 recipients and return addresses are encoded as
      EBNF.822-address.  As P1.UMPDUEnvelope.originator is encoded as
      P1.ORName, mapping 1) has already been specified.
      P1.RecipientInfo contains a P1.ORName and additional information.
      The handling of this additional information is now specified.

      4.4.1.  RFC 822 -> X.400

         The following default settings should be made for each
         component of P1.RecipientInfo.


               This can be set systematically by the X.400 system.
ToP   noToC   RFC0987 - Page 35

               Responsibility Flag should be set.  Report Request should
               be set according to content return policy, as discussed
               in section 5.3. User Report Request should be set to


               This optional component should be omitted.

      4.4.2.  X.400 -> RFC 822

         The mapping only takes place in cases where
         P1.RecipientInfo.perRecipientFlag Responsibility Flag is set.
         The following treatment should be given to the other
         P1.RecipientInfo components.


               Not used.


               If ReportRequest is Confirmed or Audit-and-Confirmed then
               a delivery report indicating success should be sent by
               the gateway. This report should use each
               P1.ReportedRecipientInfo.SupplementaryInformation to
               indicate the identity of the gateway, and the nature of
               the report (i.e. only as far as the gateway).  Failures
               will be handled by returning RFC 822 messages, and so
               User Report Request set to No report is ignored.


               If present, the O/R name should be rejected, unless the
               requested conversion can be achieved.  None of the
               currently recognised values of this parameter are
               appropriate to a gateway using this specification.
ToP   noToC   RFC0987 - Page 36
   4.5.  The full P2 / RFC 822 mapping

      All RFC 822 addresses are assumed to use the 822.mailbox syntax.
      This should include all 822.comments associated with the lexical
      tokens of the 822.mailbox.  All P2.ORNames are encoded within the
      syntax P2.ORDescriptor, or P2.Recipient (or within Message IDs).
      An asymmetrical mapping is defined between these components.

      4.5.1.  RFC 822 -> X.400

         The following sequence is followed.

            1.   Take the address, and extract an EBNF.822-address.
                 This can be derived trivially from either the
                 822.addr-spec or 822.route-addr syntax.  This is mapped
                 to P2.ORName as described above.

            2.   A string should be built consisting of (if present):

               -    The 822.phrase component if it is a 822.phrase
                    822.route-addr construct.

               -    Any 822.comments, in order, retaining the

                  This string should then be encoded into T.61 (as
                  described in chapter 3).  If the string is not null,
                  it should be assigned to P2.ORDescriptor.freeformName.

            3.   P2.ORDescriptor.telephoneNumber should be omitted.

            4.   In cases of converting to P2.Recipient,
                 P2.Recipient.replyRequest and
                 P2.Recipient.reportRequest should be omitted.

         If the construct is present, each included
         822.mailbox should be encoded as above.  The should
         be mapped to T.61, and a P2.ORDesciptor with only a
         freeformName component built from it.

      4.5.2.  X.400 -> RFC 822

         In the basic case, where P2.ORName is present, proceed as

            1.   Encode P2.ORName as EBNF.822-address.
ToP   noToC   RFC0987 - Page 37
            2a.  If P2.ORDescriptor.freeformName is present, convert it
                 to ASCII (chapter 3), and use use this as the
                 822.phrase component of 822.mailbox using the
                 822.phrase 822.route-addr construct.

            2b.  If P2.ORDescriptor.freeformName is absent, if
                 EBNF.822-address is parsed as 822.addr-spec use this as
                 the encoding of 822.mailbox. If EBNF.822-address is
                 parsed as 822.route 822.addr-spec, then a 822.phrase
                 taken from 822.local-part should be added.

            3.   If P2.ORDescriptor.telephoneNumber is present, this
                 should be placed in a trailing 822.comment.

            4.   If P2.Recipient.reportRequest has the
                 receiptNotification bit set, then an 822.comment
                 "(Receipt Notification Requested)" should be appended
                 to the address.  The effort of correlating P1 and P2
                 information is too great to justify the gateway sending
                 Receipt Notifications.

            5.   If P2.Recipient.replyRequest is present, an 822.comment
                 "(Reply requested)" or "(Reply not requested)" should
                 be appended to the address, dependent on its value.

         If P2.ORName is absent, P2.ORDescriptor.freeformName should be
         converted to ASCII, and used with the RFC 822 syntax:

            freeformname ":" ";"

         Steps 3-5 should then be followed.

   4.6.  Message IDs

      There is a need to map both ways between 822.msg-id and
      P2.IPMessageID.  A mapping is defined which is symmetrical for
      non-pathological cases.  The mapping allows for the fact that
      P2.IPMessageID.PrintableString is mandatory for the Cen/Cenelec
      profile.  This allows for good things to happen when messages pass
      multiple times across the X.400/RFC 822 boundary.  A mapping
      between 822.msg-id and P1.MPDUIdentifier is defined.  This allows
      for X.400 error messages to reference an RFC 822 ID, which is
      preferable to a gateway generated ID.
ToP   noToC   RFC0987 - Page 38
      4.6.1.  P2.IPMessageID -> 822.msg-id

         P2.IPMessageID.ORName is used to generate an 822.addr-spec, as
         defined above.  P2.IPMessageID.PrintableString is mapped to
         ASCII, as defined in chapter 3.  This string (if it is present
         and if the value is not "RFC-822") is appended to the front of
         the 822.local-part of the 822.msg-id, with "*" as a separator.
         If no ORName is present, an 822.msg-id of the form
         "PrintableString*@gateway-domain" is generated.

      4.6.2.  822.msg-id -> P2.IPMessageID

         822.local-part is parsed as:

            [ printablestring "*" ] real-local-part

         If EBNF.printablestring is found, it is mapped to
         PrintableString, and used as P2.IPMessageID.PrintableString.
         P2.IPMessageID.PrintableString is set to "RFC-822".  This
         arbitrary value allows for conformance to Cen/Cenelec.  If
         EBNF.real-local-part is not present, no P2.IPMessageID.ORName
         is generated.  Otherwise,  822.local-part is replaced with
         EBNF.real-local-part, and 822.addr-spec is mapped to
         P2.IPMessageID.ORName as defined above.

      4.6.3.  822.msg-id -> P1.MPDUIdentifier

         P1.CountryName is assigned to "", P1.AdministrationDomainName
         to 822.domain (from 822.msg-id) and P1.MPDUIdentifier.IA5String
         to 822.local-part (from 822.msg-id).

      4.6.4.  P1.MPDUIdentifier -> 822.msg-id

         822.local-part is set to P1.MPDUIdentifier.IA5String, with any
         CRLF mapped to SPACE.  If P1.CountryName is "", 822.domain is
         set to P1.AdministrationDomainName; Otherwise to
         P1.AdministrationDomainName ".." P1.CountryName.  If there are
         any specials,  the domain literal encoding should be used.
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Chapter 5 -- Protocol Elements

   This chapter gives detailed mappings for the functions outlined in
   chapters 1 and 2.  It makes extensive use of the notations and
   mappings defined in chapters 3 and 4.  This chapter is structured as

      5.1. Basic RFC 822 -> X.400 mappings

      5.2. A definition of some new RFC 822 elements, and their mapping
           to X.400.

      5.3  Some special handling associated with Return of Contents.

      5.4. X.400 -> RFC 822

   5.1.  RFC 822 -> X.400

      First, the basic functions of an 822-P1 protocol should be mapped
      as follows:

         822-P1 Originator

            Mapped to P1.UMPDUEnvelope.originator (see chapter 4).

         822-P1 Recipient

            Mapped to P1.RecipientInfo (see chapter 4).

      The RFC 822 headers are used to generate both a P1.UMPDUEnvelope
      and a P2.Heading.  The IP Message will have either one or two
      P2.BodyParts which will be type P2.IA5Text with no
      P2.IA5Text.repertoire component. The last P2.BodyPart will contain
      the RFC 822 message body.  If there are any RFC 822 headers which
      indicate mapping into the P2.BodyPart, then two P2.BodyParts are
      generated.  If a revised version of P2 allowed for extensible
      header specification, this would be seen as a preferable mapping.
      The first body part will start with the line:


      The rest of this body part will contain all of the headers not
      otherwise mapped (both 822.field-name and 822.field-body).  The
      order of any such headers should be preserved.  Similarly,
      ordering within P2.Heading and P1.UMPDUEnvelope should reflect
      ordering within the RFC 822 header.  No P1 or P2 optional fields
      are generated unless specified.
ToP   noToC   RFC0987 - Page 40
      A pro-forma X.400 message is now specified.  Some of these
      defaults may be changed by the values in the RFC 822 message being
      mapped.  The mandatory P1 and P2 components have the following


            The default should be unique value generated by the gateway.


            Always generated from 822-P1.




            These will always be supplied from 822-P1.


            The last P1.TraceInformation component is generated such
            that: P1.TraceInformation.GlobalDomainIdentifier is set to
            the local vaglue.  P1.DomainSuppliedInfo.action is set to
            relayed. P1.DomainSuppliedInfo.arrival is set to the current
            time. P1.DomainSuppliedInfo.previous may be set if there is
            anything sensible to set it to.


            The default should be a unique value generated by the

      The following optional parameters should be set:


            The P1.PerMessageFlag.contentReturnRequest bit should be set
            according to the discussion in section 5.3.  The
            P1.PerMessageFlag.alternateRecipientAllowed bit should be
            set, as it seems desirable to maximise opportunity for
            (reliable) delivery.
ToP   noToC   RFC0987 - Page 41
      The RFC 822 headings should be mapped as follows:


            Fudged onto P1.TraceInformation (try not to grimace too
            much). P1.DomainSuppliedInfo.action is set to relayed.
            P1.DomainSuppliedInfo.arrival is set to the date-time
            component P1.TraceInformation.GlobalDomainIdentifier has
            P1.CountryName as a null string, and
            P1..AdministrationDomainName as the domain of the receiving
            host (if present - null string if not).
            P1.DomainSuppliedInfo.previous has P1.CountryName as a null
            string, and P1.AdministrationDomainName has the domain of
            the sending host with all other information enclosed in
            round parentheses.  The encoding of ASCII to PrintableString
            (chapter 3) should be used if needed.  For example:

               Received: from by vax2.Cs.Ucl.AC.UK
                              with SMTP  id a002110; 18 Dec 85 10:40 GMT

                  maps to -

                     CountryName                  = ""
                     AdministrationDomainName     = "vax2.Cs.Ucl.AC.UK"
                     arrival                      = 18 Dec 85 10:40 GMT
                     action                       = relayed
                        CountryName               = ""
                        AdministrationDomainName  =
                               " (with SMTP id a002110)"


            This is used to set the first component of
            P1.TraceInformation. The mandatory components are set as

                  CountryName                  = ""
                  AdministrationDomainName     = ""
                  arrival                      = time derived from Date:
                  action                       = relayed

            No optional fields are used in the trace.
ToP   noToC   RFC0987 - Page 42

            Mapped to P2.IPMessageID.  If the RFC 822 message does not
            contain a P1-Message-ID: field, the Message-Id: field is
            also mapped to P1.MPDUIdentifier.  For these, and all other
            fields containing msg-id the mappings of chapter 4 are used
            for each msg-id.


            If Sender: is present, this is mapped to
            P2.AuthorisingUsers.  If not, it is mapped to P2.Originator.
            For this, and other components containing addresses, the
            mappings of chapter 4 are used for each address.


            Mapped to P2.Originator.


            Mapped to P2.Heading.replyToUsers.


            Mapped to P2.Heading.primaryRecipients


            Mapped to P2.Heading.copyRecipients.


            Mapped to P2.Heading.blindCopyRecipients.


            Mapped to P2.Heading.inReplyTo for the first (if any)
            822.msg-id component.  If the field contains an 822.phrase
            component, or there are multiple 822.msg-id components, the
            ENTIRE field is passed in the P2.BodyPart.


            Mapped to P2.Heading.crossReferences.
ToP   noToC   RFC0987 - Page 43

            Passed in the P2.BodyPart.


            Mapped to P2.Heading.subject.  The field-body uses the
            mapping referenced in chapter 3 from ASCII to T.61.


            Passed in the P2.BodyPart.


            Passed in the P2.BodyPart.


            Passed in the P2..BodyPart <8>.

         Other Fields

            In particular X-* fields, and "illegal" fields in common
            usage (e.g. "Fruit-of-the-day:") are passed in the
            P2.BodyPart.  The same treatment should be applied to
            RFC 822 fields where the content of the field does not
            conform to RFC 822 (e.g. a Date: field with unparsable

   5.2.  Extended RFC 822 Elements -> X.400

      First an EBNF definition of a number of extended fields is given,
      and then a mapping to X.400 is defined.  In most cases, the
      RFC 822 syntax is defined to make this mapping very
      straightforward, and so no detailed explanation of the mapping is

         extended-field  = "P1-Message-ID" ":" p1-msg-id
                         / "X400-Trace" ":" x400-trace
                         / "Original-Encoded-Information-Types"
                         / "P1-Content-Type" ":" p1-content-type
                         / "UA-Content-ID" ":" printablestring
                         / "Priority" ":" priority
                         / "P1-Recipient" : 1 mailbox
                         / "Deferred-Delivery" ":" date-time
ToP   noToC   RFC0987 - Page 44
                         / "Bilateral-Info" ":" bilateral-info
                         / "Obsoletes" ":" 1 msg-id
                         / "Expiry-Date" ":" date-time
                         / "Reply-By" ":" date-time
                         / "Importance" ":" importance
                         / "Sensitivity" ":" sensitivity
                         / "Autoforwarded" ":" boolean

         p1-msg-id       = global-id ";" *text

         p1-content-type = "P2" / atom

         x400-trace      = global-id ";"
                         "arrival" date-time
                         [ "deferred" date-time ]
                         [ "action" action ]
                         [ "converted" "(" encoded-info ")" ]
                         [ "previous" global-id ]

         action          = "Relayed" / "Rerouted" / escape

         global-id       = c "*" admd [ "*" prmd ]

         encoded-info    = 1 encoded-type

         encoded-type    = "Undefined"           ; undefined (0)
                         / "Telex"               ; tLX (1)
                         / "IA5-Text"            ; iA5Text (2)
                         / "G3-Fax"              ; g3Fax (3)
                         / "TIF0"                ; tIF0 (4)
                         / "Teletex"             ; tTX (5)
                         / "Videotex"            ; videotex (6)
                         / "Voice"               ; voice (7)
                         / "SFD"                 ; sFD (8)
                         / "TIF1"                ; tIF1 (9)
                         / escape

         priority        = "normal" / "non-urgent" / "urgent" / escape

         bilateral-info  = c "*" admd "*" *text

         importance      = "low" / "normal" / "high" / escape

         sensitivity     = "Personal" / "Private"
                         / "Company-Confidential" / escape

         escape          = 1*DIGIT
ToP   noToC   RFC0987 - Page 45
      With the exception of "Bilateral-Info:" and "X400-Trace:", there
      must be no more than one of each of these fields in an RFC 822
      header.  Any field beginning with the String "Autoforwarded-" is
      valid if the field would be syntactically valid with this string

      The mappings to X.400 are as follows:


            Mapped to P1.UMPDUEnvelope.MPDUIdentifier.  This take
            precedence over any value derived from Message-ID:.


            Mapped to the next component of
            P1.UMPDUEnvelope.Traceinformation.  Care should be taken to
            preserve order.  If one or more of these mappings is made,
            then a trace component should NOT be generated from the
            Date: field which should be redundant.  This is because the
            message has previously come from X.400, and the Date:
            information will be redundant.  Note that all trace
            information (Received: and "X400-Trace:") in the RFC 822
            message will be in strict order, with the most recent at the
            top.  This order should be preserved in the mapping.


            This is used to set P1.UMPDUEnvelope.original.
            P1.EncodedInformationTypes.[0] has bits set according to
            each of the encoded-info components in this field.  Any
            escape values should not be encoded.


            If the value is anything other than "P2", the mapping should
            not be performed (unless the new value has some semantics to
            the gateway).


            Mapped to P1.UMPDUEnvelope.UAContentID.


            Mapped to P1.UMPDUEnvelope.Priority.  An escape value should
            be encoded as P1.Priority.normal.
ToP   noToC   RFC0987 - Page 46

            If this field is set, the
            P1.PerMessageFlag.discloseRecipients bit should be set.  Any
            of the addresses here which do not correspond to 822-P1
            recipients should be added to the P1 recipient list, with
            the responsibility bit turned off.


            Mapped to P1.UMPDUEnvelope.deferredDelivery.  Note that the
            value of this field should always be in the past, as this
            field should only be present in messages which have come
            originally from X.400.  Thus there should be no implied
            action.  See also the comments on the reverse mapping.


            No attempt is made to reconvert this information back to


            Mapped to P2.Heading.obsoletes.


            Mapped to P2.Heading.expiryDate.


            Mapped to P2.Heading.replyBy.


            Mapped to P2.Heading.importance.  An escape value should be
            encoded as P2.Heading.importance.normal.


            Mapped to P2.Heading.sensitivity.  An escape value should be
            encoded as P2.Heading.sensitivity.normal.


            If this field is present and the value is "TRUE", there will
            be zero or more field names beginning "Autoforwarded-".
ToP   noToC   RFC0987 - Page 47
            These should be taken, and the string "Autoforwarded-"
            stripped.  These fields, in conjunction with the 822-P1
            information should be used to build an IP Message.  Any
            implied actions should be taken. P2.Heading.autoforwarded is
            set in this message.  The other RFC 822 fields are used to
            build another IP Message, which is used as the single body
            part of the first message.  This mechanism does not nest.

   5.3.  Return of Contents

      It is not clear how widely supported X.400 return of contents
      service will be.  However, profiling work suggests that most
      systems will not support this service.  As this service is
      expected in the RFC 822 world, two approaches are specified (it is
      not so necessary in the X.400 world, as delivery reports are
      distinguished from messages).  The choice will depend on the
      service level of the X.400 community being serviced by the

      In environments where return of contents is widely supported, the
      P1.PerMessageFlag content return request bit will be set, and the
      Report Request bit in P1.PerRecipientFlag will be set to
      Confirmed, for every message passing from RFC 822 -> X.400.  The
      content return service can then be passed back to the end
      (RFC 822) user in a straightforward manner.

      In environments where return of contents is not widely supported,
      a gateway must make special provisions to handle return of
      contents.  For every message passing from RFC 822 -> X.400, the
      P1.PerMessageFlag content return request bit will be set, and the
      Report Request bit in P1.PerRecipientFlag will be set to
      Confirmed.  When the delivery report comes back, the gateway can
      note that the message has been delivered to the recipient(s) in
      question.  If a non-delivery report is received, a meaningful
      report (containing some or all of the original message) can be
      sent to the 822-P1 originator.  If no report is received for a
      recipient, a (timeout) failure notice should be sent to the 822-P1
      originator.  The gateway may retransmit the X.400 message if it
      wishes.  Delivery confirmations should only be sent back to the
      822-P1 originator if the P1.PerRecipientFlag User Report Request
      bit is set to Confirmed.
ToP   noToC   RFC0987 - Page 48
   5.4.  X.400 -> RFC 822

      5.4.1.  General

         This section describes how to build a pro-forma message, and
         then explains how these defaults may be overridden.  It should
         be noted that RFC 822 folding of headers should be used in an
         appropriate manner.

      5.4.2.  Service MPDU

            Any P1.ProbeMPDU should be serviced by the gateway, as there
            is no equivalent RFC 822 functionality.  The value of the
            reply is dependent on whether the gateway could service a
            User MPDU with the values specified in the probe.  The reply
            should make use of P1.SupplementaryInformation to indicate
            that the probe was serviced by the gateway.
  Delivery Report

            The 822-P1 components are constructed as follows:

               822-P1 Originator

                  This is set to an 822.addr-spec pointing to an
                  administrator at the gateway.

               822-P1 Recipient

                  The single recipient is constructed from
                  P1.DeliveryReportEnvelope.originator, using the
                  mappings of chapter 4.

            The mandatory RFC 822 headers for an RFC 822 pro-forma are
            constructed as follows:


                  From the P1.DomainSuppliedInfo.arrival component of
                  the first P1.TraceInformation component.


                  This is set to the same as the 822-P1 originator.  An
ToP   noToC   RFC0987 - Page 49
                  appropriate phrase component may be added (e.g. giving
                  the name of the gateway).


                  The same as the 822-P1 recipient.

            A Subject: field should be added, which contains some
            appropriate words (e.g. "Delivery Report").

            The other two P1.DeliveryReportEnvelope parameters should be
            mapped as follows:


                  This should be mapped to a P1-Message-Id: field.


                  Each component should be mapped to an "X400-Trace:"
                  field.  RFC 822 and X.400 ordering should be
                  maintained (see 5.3).

            The P1.DeliveryReportContent parameters should be mapped to
            a series of new RFC 822 headers.  These new headers are
            intended for processing in the RFC 822 world.  No attempt
            will be made to reverse the mappings.

               drc-field    = "Delivery-Report-Content-Original"
                           ":" msg-id
                 / "Delivery-Report-Content-Intermediate-Trace"
                           ":" x400-trace
                 / "Delivery-Report-Content-UA-Content-ID"
                           ":" printablestring
                 / "Delivery-Report-Content-Billing-Information"
                           ":" *text
                 / "Delivery-Report-Content-Reported-Recipient-Info"
                           ":" drc-info

               drc-info     = mailbox ";"
                            last-trace ";"
                            "ext" 1*DIGIT
                            "flags" 2DIGIT
                            [ "intended" mailbox ] ";"
                            [ "info" printablestring ]
ToP   noToC   RFC0987 - Page 50
               last-trace   = drc-report ";"
                            date-time ";"
                            [ "converted" "(" encoded-info ")"

               drc-report   = "SUCCESS" drc-success
                            / "FAILURE" drc-failure

               drc-success  = date-time ";" 1*DIGIT

               drc-failure  = *text [ ";" *text ] ";"

            There may be multiple
            "Delivery-Report-Content-Intermediate-Trace:" and
            "Delivery-Report-Content-Reported-Recipient-Info:" fields.
            The msg-id for "Delivery-Report-Content-Original" is derived
            according to the mapping of chapter 4.  EBNF.drc-failure may
            use numeric values or textual explanation.  The latter is
            preferred.  All P1.DeliveryReportContent parameters are
            mapped to the corresponding component.  The order of
            "Delivery-Report-Content-Intermediate-Trace:" should have
            the most recently stamped one first.

            The body of the RFC 822 message should be a human readable
            description of the critical parts of the
            P1.DeliveryReportContent.  In particular, the failed
            recipients, and failure reason should be given.  Some or all
            of the original message should be included in the delivery
            report. The original message will be available at the
            gateway, as discussed in section 5.3.

      5.4.3.  User MPDU

         These elements are the basis for both Status Report and IP

         The 822-P1 components are constructed as follows:

            822-P1 Originator

               This is derived from P1.UMPDUEnvelope.originator.

            822-P1 Recipient

               Each recipient is constructed from the P1.RecipientInfo,
               as described in chapter 4.  This describes actions as
               well as format mappings.
ToP   noToC   RFC0987 - Page 51
         The mandatory RFC 822 field pro-forma is derived as follows.
         In most cases where the P1.UMPDUContent is an IP Message, these
         defaults will be overridden:


               From the P1.DomainSuppliedInfo.arrival component of the
               first P1.TraceInformation component.


               From the P1.UMPDUEnvelope.originator, as defined in
               chapter 4.


               This default is only required if the generated RFC 822
               message has no destination specification.  If
               P1.PerMessageFlag.discloseRecipients is set then it
               should contain the ORName in each P1.RecipientInfo
               component.  If it is not set, the it should be set to
               "To: No Recipients Specified : ;".

         The mappings, and any actions for each P1.UserMPDU element is
         now considered.


               Mapped to the extended RFC 822 field "P1-Message-ID:".
               Note that the sequence CRLF is mapped to SPACE, which
               makes the mapping irreversible for such cases.


               Mapped to the extended RFC 822 field
               "Original-Encoded-Information-Types:".  If it contains
               only P2.IA5Text, the RFC 822 field may be omitted.


               As this can currently only have one value, it is not
               mapped, on the basis that it is redundant.  If the field
               contains any value other than P2, then the UMPDU should
               be rejected.
ToP   noToC   RFC0987 - Page 52

               Mapped to the extended RFC 822 field "UA-Content-Id:".


               Mapped to the extended RFC 822 field "Priority:".


               This has a number of components:

                  - discloseRecipients

                     If this bit is set, a "P1-Recipient:" field should
                     be generated, and contain each of the P1

                  - conversionProhibited

                     If this bit is set, the message should be rejected
                     if it contains P2.BodyPart which is not P2.IA5Text
                     or P2.ForwardedIPMessage.

                  - alternateRecipientAllowed

                     The value of this bit is ignored.

                  - contentReturnRequest

                     The value of this bit is ignored.


               This should be mapped to the extended RFC 822 field
               "Deferred-Delivery:".  X.400 profiles, and in particular
               the CEN/CENELEC profile [CEN/CENELEC/85a], specify that
               this element must be supported at the first MTA.  Thus,
               it is expected that the value of this element will always
               be in the past.  If it is not, the function may
               optionally be implemented by the gateway: that is, the
               gateway should hold the message until the time specified
               in the protocol element.  Thus the extended RFC 822 field
               is just for information.
ToP   noToC   RFC0987 - Page 53

               Each component should be encoded in the extended RFC 822
               field "Bilateral-Info:".  P1.BilateralInfo should be
               mapped into ASCII in a manner appropriate to its
               contents.  This submapping is not reversible.


               This should be mapped to "X400-Trace:", as for the
               delivery report.

      5.4.4.  Status Report

         The entire status report is mapped into the body of the RFC 822
         message, in the same manner as for a Delivery Report.  An
         appropriate "Subject:" field should be generated.  As status
         reports cannot be requested from the RFC 822 world, the mapping
         is not likely to be used a great deal.

      5.4.5.  IP Message

         The P1.UMPDUEnvelope pro-forma specification ensures all the
         822-P1 information, and a minimal (legal) RFC 822 message.  The
         mappings and actions for the P2.Heading components are now
         described.  Basically, these are interpreted as actions and/or
         mappings into RFC 822 fields. The following mappings are


               This is mapped to the field "Message-ID:", according to
               section 4.


               If P2.Heading.authorisingUsers is present this is mapped
               to Sender:, if not to From:.


               Mapped to From:.


               Mapped to To:.
ToP   noToC   RFC0987 - Page 54

               Mapped to Cc:.


               Mapped to Bcc:.


               Mapped to In-Reply-To:.


               Mapped to the extended RFC 822 field "Obsoletes:"


               Mapped to References:.


               Mapped to subject.  The contents are converted to ASCII
               (as defined in chapter 3).  Any CRLF are not mapped, but
               are used as points at which the subject field must be
               folded.  line.


               Mapped to the extended RFC 822 field "Expiry-Date:".


               Mapped to the extended RFC 822 field "Reply-By:".


               Mapped to Reply-To:.


               Mapped to the extended RFC 822 field "Importance:".


               Mapped to the extended RFC 822 field "Sensitivity:".
ToP   noToC   RFC0987 - Page 55

               If it is set to FALSE, it is simply mapped to the
               extended RFC 822 field "Autoforwarded:".  If this is set
               to TRUE, the P2.Body does not consist of a single
               P2.ForwardedIPMessage, then there is an X.400 error, and
               the message should be bounced.  Otherwise the following
               steps are taken.

                  1.  The mappings for all of the message, except the
                      body part are completed.

                  2.  Prepend each RFC 822 fieldname with the string
                      "Autoforwarded-". Mapped to the extended RFC 822
                      field "Autoforwarded:".

                  3.  Add the field "Autoforwarded:" with value TRUE.

                  4.  Convert the syntax of the P2.ForwardedIPMessage to
                      generate the remaining RFC 822 fields.

         The P2.Body is mapped into the RFC 822 message body.  Each
         P2.BodyPart is converted to ASCII.  If the P2.Body contains a
         P2.BodyPart not listed here, the entire message should be
         rejected.  If there are exactly two P2.IA5Text body parts, and
         the first line of the first is "RFC-822-Headers:", then the
         rest of this first body part should be treated as additional
         header information for the RFC 822 message.  If there is an
         "In-Reply-To:" field, this should be used to replace any
         generated In-Reply-To: field.

         In other cases of multiple P2.BodyPart, the mapping defined by
         Rose and Stefferud in [Rose85b], should be used to separate the
         P2.BodyParts in the single RFC 822 message body.

         Individual body parts are mapped as follows:


               The mapping is trivial.


               If any P1.Teletex.NonBasicParams are set, the message
               should be rejected.  Otherwise, it should be converted to
               ASCII according to chapter 3.
ToP   noToC   RFC0987 - Page 56

               An SFD should be converted to ASCII as if it was being
               rendered on an 79 column ASCII only VDU.  It seems likely
               that many gateways will not support this conversion.  In
               these cases, the message should be rejected.


               The and
               P2.ForwardedIPMessage.DeliveryInformation are
               discarded <9>.  The IM-UAPDU should have its syntax
               mapped (recursively) according to this gatewaying
               specification.  Clearly, it makes no sense to apply any
               of the actions defined here.
ToP   noToC   RFC0987 - Page 57
Appendix A -- Quoted String Encodings

   This Appendix describes a quoting mechanism which may be used to
   allow general interworking between RFC 822, and variants of RFC 822
   which do not support 822.quoted-string.  This is important, as the
   basic X.400 <-> RFC 822 mapping makes use of 822.quoted-string.

   1.  ASCII <-> 822.atom

      The following EBNF is specified.

         atom-encoded    = *( a-char / a-encoded-char )
         a-char          = <any CHAR except specials, SPACE,
                                 CTL, "_", and "#">
         a-encoded-char  = "_"                   ; (space)
                         / "#u#"                 ; (_)
                         / "#l#"                 ; <(>
                         / "#r#"                 ; <)>
                         / "#m#"                 ; (,)
                         / "#c#"                 ; (:)
                         / "#b#"                 ; (\)
                         / "#h#"                 ; (#)
                         / "#e#"                 ; ($=)
                         / "#s#"                 ; ($/)
                         / "#" 3DIGIT "#"

      NOTE: There are two encodings of double characters.  This is so
      that systems using this encoding, do not also need to know about
      the "$" quoting mechanism defined in chapter 4.

      The 822.3DIGIT in EBNF.a-encoded-char must have range 0-127
      (Decimal), and is interpreted in decimal as the corresponding
      ASCII character.  The choice of special abbreviations (as opposed
      to octal encoding) provided is based on the manner in which this
      mapping is most frequently used: encoding PrintableString
      components of O/R names as atom.  Therefore, there are special
      encodings for each of the PrintableString characters not in
      EBNF.a-char, except ".".  Space is given a single character
      encoding, due to its (expected) frequency of use, and backslash as
      the RFC 822 single quote character.

      To encode (ASCII -> atom): all EBNF.a-char are used directly and
      all other CHAR are encoded as EBNF.a-encoded-char.  To decode
      (822.atom -> ASCII): if 822.atom can be parsed as
      EBNF.encoded-atom reverse the previous mapping.  If it cannot be
      so parsed, map the characters directly.
ToP   noToC   RFC0987 - Page 58
   2.  822.local-part <-> ASCII

      A related transformation is for 822.local-part (or other element
      defined as '822.word ("." 822.word)') where not 822.quoted-text is
      used.  To encode (ASCII -> 822.local-part), all EBNF.a-char and
      "." are used directly and all other 822.CHAR are encoded as
      EBNF.a-encoded-char.  To decode (822.local-part -> ASCII), first
      attempt to parse 822.local-part as '822.atom *("." 822.atom)'.  If
      this fails, or if each 822.atom cannot be parsed as
      EBNF.atom-encoded then map each character directly.  Otherwise map
      each "." directly, and each atom as in the previous section.

      There are places where it is needed to convert between
      PrintableString or IA5Text (X.400), and 822.word (RFC 822).  word
      may be encoded as 822.atom (which has a restricted character set)
      or as 822.quoted-string, which can handle all ASCII characters.
      If 822.quoted-string is used, clearly the mappings for
      PrintableString defined in Chapter 3 provide a straightforward
      mapping.  However, some RFC 822 based networks cannot handle the
      822.quoted-string format in all cases.  This Appendix is for use
      in these cases.  The major requirement for this mapping is the
      UNIX world, but it may well be needed in other places.

      These mappings are somewhat artificial, and their usage is
      discouraged, except in cases where there is no alternative.
ToP   noToC   RFC0987 - Page 59
Appendix B -- Mappings Specific to JNT Mail

   This Appendix is specific to the JNT Mail Protocol.  It describes
   specific changes in the context of this protocol.  Addressing is not
   discussed here, as it is covered in Appendix A.

   1.  Introduction

      There are four aspects of a gateway which are JNT Mail Specific,
      in addition to those relating to addressing.  These are each given
      a section of this appendix.

   2.  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

      When going from JNT Mail to X.400, the User Report Request bits of
      each P1.RecipientInfo.perRecipientFlag should be set to confirmed.
      If there is more that one address in the Acknowledge-To: field, or
      if the one address is not equivalent to the 822-P1 return address,

         a.   Acknowledgement(s) should be generated by the gateway.
              The text of these acknowledgements should indicate that
              they are generated by the gateway.

         b.   The Acknowledge-To: field should also be passed in the
              first P2.BodyPart.

      When going from X.400 to JNT Mail, in cases where
      P1.RecipientInfo.perRecipientFlag has the user bits set to
      confirmed the copy of the message to that recipient should have an
      Acknowledge-To: field containing the P.UMPDUEnvelope.originator.
      No attempt should be made to map Receipt notification requests
      onto Acknowledge-To:.  This is because no association can be
      guaranteed between P2 and P1 level addressing information.

   3.  Trace

      JNT Mail trace uses the Via: syntax.  When going from JNT Mail to
      X.400, the following mapping onto P1.TraceInformation is used.

         P1.DomainSuppliedInfo.action is set to relayed.

         P1.DomainSuppliedInfo.arrival is set to the date-time component
ToP   noToC   RFC0987 - Page 60
         of the Via: field.  P1.DomainSuppliedInfo.previous has
         P1.CountryName as a null string, and
         P1.AdministrationDomainName as the domain specified in the Via:
         P1.TraceInformation.GlobalDomainIdentifier has P1.CountryName
         as a null string, and P1.AdministrationDomainName as any
         commented information in the Via: field.  For example:

            Via: UK.AC.Edinburgh ; 17 Jun 85 9:15:29 BST (EMAS V7)

            maps to -

               CountryName                  = ""
               AdministrationDomainName     = "(EMAS V7)"
               arrival                      = 17 Jun 85 9:15:29 BST
               action                       = relayed
                  CountryName               = ""
                  AdministrationDomainName  = "UK.AC.Edinburgh"

   4.  Timezone specification

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

   5.  Lack of separate 822-P1 originator specification

      In JNT Mail the default mapping of the P1.MPDUEnvelope.originator
      is to the Sender: field.  This can cause a problem if the mapping
      of P2.Heading has already generated a Sender: field.  To overcome
      this, new extended JNT Mail field is defined.  This is chosen to
      align with the JNT recommendation for interworking with full
      RFC 822 systems [Kille84b].

         original-sender     = "Original-Sender" ":" mailbox

      If an IPM has no P2.heading.authorisingUsers component and
      P2.Heading.originator.ORName is different from
      P1.UMPDUEnvelope.originator, map P1.MPDUEnvelope.originator onto
      the Sender: field.

      If an IPM has a P2.heading.authorisingUsers component, and
      P2.Heading.originator.ORName is different from
      P1.UMPDUEnvelope.originator, P1.MPDUEnvelpoe.originator should be
ToP   noToC   RFC0987 - Page 61
      mapped onto the Sender: field, and P2.Heading.originator mapped
      onto the Original-Sender: field.

      In other cases the P1.MPDUEnvelope.Originator is already correctly

      Note that in some pathological cases, this mapping is
ToP   noToC   RFC0987 - Page 62
Appendix C -- Mappings Specific to Internet Mail

   The Simple Mail Transfer Protocol [Postel82a] is used in the
   ARPA-Internet, and in any network following the US DoD standards for
   internetwork protocols.  This appendix is specific to those hosts
   which use SMTP to exchange mail.

   1.   Mapping between O/R names and SMTP addresses

      The mappings of Chapter 4 are to be used.

   2.   Use of the ARPA Domain System

      Whenever possible, domain-qualified addresses should be be used to
      specify encoded O/R names.  These domain encodings naturally
      should be independent of any routing information.

   3.   Identification of gateways

      The ARPA-Internet Network Information Center (NIC) will maintain a
      list of registered X.400 gateways in the ARPA Internet.
ToP   noToC   RFC0987 - Page 63
Appendix D -- Mappings Specific to Phonenet Mail

   There are currently no mappings specific to Phonenet Mail.
ToP   noToC   RFC0987 - Page 64
Appendix E -- Mappings Specific to UUCP Mail

   Gatewaying of UUCP and X.400 is handled by first gatewaying the UUCP
   address into RFC 822 syntax (using RFC 976) [Horton86a] and then
   gatewaying the resulting RFC 822 address into X.400.  For example, an
   X.400 address

      Country         US
      Organization    Xerox
      Personal Name   John Smith

   might be expressed from UUCP as


   (assuming gate is a UUCP-ARPA gateway and gatehost.COM is an
   ARPA-X.400 gateway) or


   (assuming that Xerox.COM and /C=US/O=Xerox/ are equivalent.)

   In the other direction, a UUCP address Smith@ATT.COM, integrated into
   822, would be handled as any other 822 address.  A non-integrated
   address such as inthop!dest!user might be handled thought a pair of

      Country         US
      ADMD            ATT
      PRMD            ARPA
      Organization    GateOrg
      RFC-822         inthop!dest!user@gatehost.COM

   or through a single X.400 to UUCP gateway:

      Country         US
      ADMD            ATT
      PRMD            UUCP
      Organization    GateOrg
      UUCP            inthop!dest!user
ToP   noToC   RFC0987 - Page 65
Appendix F -- Format of Address Mapping Tables

   There is a need to specify the association between the domain and
   X.400 namespaces described in 4.2.1.  This is defined as a table
   syntax, but the syntax is defined in a manner which makes it suitable
   for use with domain nameservers (such as the DARPA Domain nameservers
   or the UK NRS).  The symmetry of the mapping is not clear, so a
   separate table is specified for each direction.  For domain -> X.400:

      domain-syntax "#" dmn-orname "#"

      For example:


   For X.400 -> domain:

      dmn-orname "#" domain-syntax "#"

   EBNF.domain-syntax will be interpreted according to RFC 920.
   EBNF.dmn-orname will have components ordered as defined in section
   4.2.1, and with the most significant component on the RHS.
ToP   noToC   RFC0987 - Page 66


      K.H. Bonacker, U. Pankoke-Babatz, and H. Santo, "EAN - Conformity
      to X.400 and DFN-Pflichtenheft," GMD (Gesellschaft fur Mathematik
      und Datenverarbeitung) report, June 1985.


      CCITT SG 5/VII, "Recommendations X.400," Message Handling Systems:
      System Model - Service Elements, October 1984.


      CCITT SG 5/VII, "Recommendations X.411," Message Handling Systems:
      Message Transfer Layer, October 1984.


      CCITT SG 5/VII, "Recommendations X.420," Message Handling Systems:
      Interpersonal Messaging User Agent Layer, October 1984.


      CCITT SG 5/VII, "Recommendations X.409," Message Handling Systems:
      Presentation Transfer Syntax and Notation, October 1984.


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


      D.H. Crocker, "Standard of the Format of ARPA Internet Text
      Messages," RFC 822, August 1982.


      M.R. Horton, "Draft Standard for ARPA/MHS Addressing Gateways,"
      AT&T Bell Laboratories, October 1985.
ToP   noToC   RFC0987 - Page 67

      M.R. Horton, "UUCP Mail Interchange Format Standard", RFC 976,
      February 1986.


      ICL, "Comparison of service elements of Grey Book Mail and X.400,"
      Mailgroup Note 18: Extract from unpublished report for ITSU
      (Information Technology Standards Unit), July 1984.


      S.E. Kille, (editor), JNT Mail Protocol (revision 1.0), Joint
      Network Team, Rutherford Appleton Laboratory, March 1984.


      S.E. Kille, "Gatewaying between RFC 822 and JNT Mail," JNT
      Mailgroup Note 15, May 1984.


      S.E. Kille, "O/R Names in the UK Academic Community," UK Working
      Document, March 1986.


      J. Larmouth, "JNT Name Registration Technical Guide," Salford
      University Computer Centre, April 1983.


      G. Neufeld, J. Demco, B. Hilpert, and R. Sample, "EAN: an X.400
      message system," in Second International Symposium on Computer
      Message Systems, Washington, pp. 1-13, North Holland,
      September 1985.


      J. Postel, "Simple Mail Transfer Protocol," RFC 821, August 1982.


      J. Postel and J. Reynolds, "Domain Requirements," RFC 920,
      October 1984.
ToP   noToC   RFC0987 - Page 68

      M.T. Rose, "Mapping Service Elements between ARPA and MHS," Draft
      proposal, October 1985.


      M.T. Rose and E.A. Stefferud, "Proposed Standard for Message
      Encapsulation," RFC 934, January 1985.
ToP   noToC   RFC0987 - Page 69

   <0>  UNIX is a trademark of Bell Laboratories.

   <1>  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.  (Sometime called
        a "mail relay".)

   <2>  If the remote protocol is JNT Mail, a notification may also be
        sent by the recipient UA.

   <3>  The asymmetry occurs where an ASCII string contains the sequence  This would be mapped directly to
        PrintableString, but the reverse mapping would be to the value
        implied by the sequence.

   <4>  It might be suggested that for reasons of elegance, (left parenthesis) is encoded as This is not done, as it it would never be
        possible to represent a PrintableString containing the character
        "(" in ASCII.  This is because an "(" in ASCII would be mapped
        to the encoding in PrintableString.

   <5>  In practice, a gateway will need to parse various illegal
        variants on  In cases where cannot
        be parsed, it is recommended that the derived UTCTime is set to
        the value at the time of translation.

   <6>  P2.ORname is defined as P1.ORName.

   <7>  This recommendation may change in the light of CCITT or
        CEN/CENELEC guidelines on the use of initials.

   <8>  It would be possible to use a ForwardedIPMessage for these
        fields, but the semantics are (arguably) slightly different, and
        it is probably not worth the effort.

   <9>  Although this violates chapter 1, part 4, principles 2 and 3, it
        is suggested that this is justified by principle 1.