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From: brian@sdcc3.UUCP (Brian Kantor)
Newsgroups: net.sources
Subject: RFC822 (Mail Standards) [pt 2 of 2] (last of series)
Message-ID: <2633@sdcc3.UUCP>
Date: Tue, 15-Jan-85 18:01:30 EST
Article-I.D.: sdcc3.2633
Posted: Tue Jan 15 18:01:30 1985
Date-Received: Fri, 18-Jan-85 01:17:10 EST
Organization: UCSD wombat breeding society
Lines: 1392



 
     Standard for ARPA Internet Text Messages


        each receive new message identifiers.

     4.6.2.  IN-REPLY-TO

             The contents of this field identify  previous  correspon-
        dence  which this message answers.  Note that if message iden-
        tifiers are used in this  field,  they  must  use  the  msg-id
        specification format.

     4.6.3.  REFERENCES

             The contents of this field identify other  correspondence
        which  this message references.  Note that if message identif-
        iers are used, they must use the msg-id specification format.

     4.6.4.  KEYWORDS

             This field contains keywords  or  phrases,  separated  by
        commas.

     4.7.  OTHER FIELDS

     4.7.1.  SUBJECT

             This is intended to provide a summary,  or  indicate  the
        nature, of the message.

     4.7.2.  COMMENTS

             Permits adding text comments  onto  the  message  without
        disturbing the contents of the message's body.

     4.7.3.  ENCRYPTED

             Sometimes,  data  encryption  is  used  to  increase  the
        privacy  of  message  contents.   If the body of a message has
        been encrypted, to keep its contents private, the  "Encrypted"
        field  can be used to note the fact and to indicate the nature
        of the encryption.  The first  parameter  indicates  the
        software  used  to  encrypt the body, and the second, optional
         is intended to  aid  the  recipient  in  selecting  the
        proper  decryption  key.   This  code word may be viewed as an
        index to a table of keys held by the recipient.

        Note:  Unfortunately, headers must contain envelope,  as  well
               as  contents,  information.  Consequently, it is neces-
               sary that they remain unencrypted, so that  mail  tran-
               sport   services   may   access   them.   Since  names,
               addresses, and "Subject"  field  contents  may  contain


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               sensitive  information,  this  requirement limits total
               message privacy.

             Names of encryption software are registered with the Net-
        work  Information Center, SRI International, Menlo Park, Cali-
        fornia.

     4.7.4.  EXTENSION-FIELD

             A limited number of common fields have  been  defined  in
        this  document.   As  network mail requirements dictate, addi-
        tional fields may be standardized.   To  provide  user-defined
        fields  with  a  measure  of  safety,  in name selection, such
        extension-fields will never have names  that  begin  with  the
        string "X-".

             Names of Extension-fields are registered with the Network
        Information Center, SRI International, Menlo Park, California.

     4.7.5.  USER-DEFINED-FIELD

             Individual users of network mail are free to  define  and
        use  additional  header  fields.   Such fields must have names
        which are not already used in the current specification or  in
        any definitions of extension-fields, and the overall syntax of
        these user-defined-fields must conform to this specification's
        rules   for   delimiting  and  folding  fields.   Due  to  the
        extension-field  publishing  process,  the  name  of  a  user-
        defined-field may be pre-empted

        Note:  The prefatory string "X-" will never  be  used  in  the
               names  of Extension-fields.  This provides user-defined
               fields with a protected set of names.


















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     5.  DATE AND TIME SPECIFICATION

     5.1.  SYNTAX

     date-time   =  [ day "," ] date time        ; dd mm yy
                                                 ;  hh:mm:ss zzz

     day         =  "Mon"  / "Tue" /  "Wed"  / "Thu"
                 /  "Fri"  / "Sat" /  "Sun"

     date        =  1*2DIGIT month 2DIGIT        ; day month year
                                                 ;  e.g. 20 Jun 82

     month       =  "Jan"  /  "Feb" /  "Mar"  /  "Apr"
                 /  "May"  /  "Jun" /  "Jul"  /  "Aug"
                 /  "Sep"  /  "Oct" /  "Nov"  /  "Dec"

     time        =  hour zone                    ; ANSI and Military

     hour        =  2DIGIT ":" 2DIGIT [":" 2DIGIT]
                                                 ; 00:00:00 - 23:59:59

     zone        =  "UT"  / "GMT"                ; Universal Time
                                                 ; North American : UT
                 /  "EST" / "EDT"                ;  Eastern:  - 5/ - 4
                 /  "CST" / "CDT"                ;  Central:  - 6/ - 5
                 /  "MST" / "MDT"                ;  Mountain: - 7/ - 6
                 /  "PST" / "PDT"                ;  Pacific:  - 8/ - 7
                 /  1ALPHA                       ; Military: Z = UT;
                                                 ;  A:-1; (J not used)
                                                 ;  M:-12; N:+1; Y:+12
                 / ( ("+" / "-") 4DIGIT )        ; Local differential
                                                 ;  hours+min. (HHMM)

     5.2.  SEMANTICS

          If included, day-of-week must be the day implied by the date
     specification.

          Time zone may be indicated in several ways.  "UT" is Univer-
     sal  Time  (formerly called "Greenwich Mean Time"); "GMT" is per-
     mitted as a reference to Universal Time.  The  military  standard
     uses  a  single  character for each zone.  "Z" is Universal Time.
     "A" indicates one hour earlier, and "M" indicates 12  hours  ear-
     lier;  "N"  is  one  hour  later, and "Y" is 12 hours later.  The
     letter "J" is not used.  The other remaining two forms are  taken
     from ANSI standard X3.51-1975.  One allows explicit indication of
     the amount of offset from UT; the other uses  common  3-character
     strings for indicating time zones in North America.


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     6.  ADDRESS SPECIFICATION

     6.1.  SYNTAX

     address     =  mailbox                      ; one addressee
                 /  group                        ; named list

     group       =  phrase ":" [#mailbox] ";"

     mailbox     =  addr-spec                    ; simple address
                 /  phrase route-addr            ; name & addr-spec

     route-addr  =  "<" [route] addr-spec ">"

     route       =  1#("@" domain) ":"           ; path-relative

     addr-spec   =  local-part "@" domain        ; global address

     local-part  =  word *("." word)             ; uninterpreted
                                                 ; case-preserved

     domain      =  sub-domain *("." sub-domain)

     sub-domain  =  domain-ref / domain-literal

     domain-ref  =  atom                         ; symbolic reference

     6.2.  SEMANTICS

          A mailbox receives mail.  It is a  conceptual  entity  which
     does  not necessarily pertain to file storage.  For example, some
     sites may choose to print mail on their line printer and  deliver
     the output to the addressee's desk.

          A mailbox specification comprises a person, system  or  pro-
     cess name reference, a domain-dependent string, and a name-domain
     reference.  The name reference is optional and is usually used to
     indicate  the  human name of a recipient.  The name-domain refer-
     ence specifies a sequence of sub-domains.   The  domain-dependent
     string is uninterpreted, except by the final sub-domain; the rest
     of the mail service merely transmits it as a literal string.

     6.2.1.  DOMAINS

        A name-domain is a set of registered (mail)  names.   A  name-
        domain  specification  resolves  to  a subordinate name-domain
        specification  or  to  a  terminal  domain-dependent   string.
        Hence,  domain  specification  is  extensible,  permitting any
        number of registration levels.


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        Name-domains model a global, logical, hierarchical  addressing
        scheme.   The  model is logical, in that an address specifica-
        tion is related to name registration and  is  not  necessarily
        tied  to  transmission  path.   The  model's  hierarchy  is  a
        directed graph, called an in-tree, such that there is a single
        path  from  the root of the tree to any node in the hierarchy.
        If more than one path actually exists, they are considered  to
        be different addresses.

        The root node is common to all addresses; consequently, it  is
        not  referenced.   Its  children  constitute "top-level" name-
        domains.  Usually, a service has access to its own full domain
        specification and to the names of all top-level name-domains.

        The "top" of the domain addressing hierarchy -- a child of the
        root  --  is  indicated  by  the right-most field, in a domain
        specification.  Its child is specified to the left, its  child
        to the left, and so on.

        Some groups provide formal registration services;  these  con-
        stitute   name-domains   that  are  independent  logically  of
        specific machines.  In addition, networks and machines  impli-
        citly  compose name-domains, since their membership usually is
        registered in name tables.

        In the case of formal registration, an organization implements
        a  (distributed)  data base which provides an address-to-route
        mapping service for addresses of the form:

                         person@registry.organization

        Note that "organization" is a logical  entity,  separate  from
        any particular communication network.

        A mechanism for accessing "organization" is universally avail-
        able.   That mechanism, in turn, seeks an instantiation of the
        registry; its location is not indicated in the address specif-
        ication.   It  is assumed that the system which operates under
        the name "organization" knows how to find a subordinate regis-
        try.  The registry will then use the "person" string to deter-
        mine where to send the mail specification.

        The latter,  network-oriented  case  permits  simple,  direct,
        attachment-related address specification, such as:

                              user@host.network

        Once the network is accessed, it is expected  that  a  message
        will  go  directly  to the host and that the host will resolve


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        the user name, placing the message in the user's mailbox.

     6.2.2.  ABBREVIATED DOMAIN SPECIFICATION

        Since any number of  levels  is  possible  within  the  domain
        hierarchy,  specification  of  a  fully  qualified address can
        become inconvenient.  This standard permits abbreviated domain
        specification, in a special case:

            For the address of  the  sender,  call  the  left-most
            sub-domain  Level  N.   In a header address, if all of
            the sub-domains above (i.e., to the right of) Level  N
            are  the same as those of the sender, then they do not
            have to appear in the specification.   Otherwise,  the
            address must be fully qualified.

            This feature is subject  to  approval  by  local  sub-
            domains.   Individual  sub-domains  may  require their
            member systems, which originate mail, to provide  full
            domain  specification only.  When permitted, abbrevia-
            tions may be present  only  while  the  message  stays
            within the sub-domain of the sender.

            Use of this mechanism requires the sender's sub-domain
            to reserve the names of all top-level domains, so that
            full specifications can be distinguished from abbrevi-
            ated specifications.

        For example, if a sender's address is:

                 sender@registry-A.registry-1.organization-X

        and one recipient's address is:

                recipient@registry-B.registry-1.organization-X

        and another's is:

                recipient@registry-C.registry-2.organization-X

        then ".registry-1.organization-X" need not be specified in the
        the  message,  but  "registry-C.registry-2"  DOES  have  to be
        specified.  That is, the first two addresses may  be  abbrevi-
        ated, but the third address must be fully specified.

        When a message crosses a domain boundary, all  addresses  must
        be  specified  in  the  full format, ending with the top-level
        name-domain in the right-most field.  It is the responsibility
        of  mail  forwarding services to ensure that addresses conform


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        with this requirement.  In the case of abbreviated  addresses,
        the  relaying  service must make the necessary expansions.  It
        should be noted that it often is difficult for such a  service
        to locate all occurrences of address abbreviations.  For exam-
        ple, it will not be possible to find such abbreviations within
        the  body  of  the  message.   The "Return-Path" field can aid
        recipients in recovering from these errors.

        Note:  When passing any portion of an addr-spec onto a process
               which  does  not interpret data according to this stan-
               dard (e.g., mail protocol servers).  There must  be  NO
               LWSP-chars  preceding  or  following the at-sign or any
               delimiting period ("."), such as  shown  in  the  above
               examples,   and   only  ONE  SPACE  between  contiguous
               s.

     6.2.3.  DOMAIN TERMS

        A domain-ref must be THE official name of a registry, network,
        or  host.   It  is  a  symbolic  reference, within a name sub-
        domain.  At times, it is necessary to bypass standard  mechan-
        isms  for  resolving  such  references,  using  more primitive
        information, such as a network host address  rather  than  its
        associated host name.

        To permit such references, this standard provides the  domain-
        literal  construct.   Its contents must conform with the needs
        of the sub-domain in which it is interpreted.

        Domain-literals which refer to domains within the ARPA  Inter-
        net  specify  32-bit  Internet addresses, in four 8-bit fields
        noted in decimal, as described in Request for  Comments  #820,
        "Assigned Numbers."  For example:

                                 [10.0.3.19]

        Note:  THE USE OF DOMAIN-LITERALS IS STRONGLY DISCOURAGED.  It
               is  permitted  only  as  a means of bypassing temporary
               system limitations, such as name tables which  are  not
               complete.

        The names of "top-level" domains, and  the  names  of  domains
        under  in  the  ARPA Internet, are registered with the Network
        Information Center, SRI International, Menlo Park, California.

     6.2.4.  DOMAIN-DEPENDENT LOCAL STRING

        The local-part of an  addr-spec  in  a  mailbox  specification
        (i.e.,  the  host's  name for the mailbox) is understood to be


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        whatever the receiving mail protocol server allows.  For exam-
        ple,  some systems do not understand mailbox references of the
        form "P. D. Q. Bach", but others do.

        This specification treats periods (".") as lexical separators.
        Hence,  their  presence  in  local-parts which are not quoted-
        strings, is detected.   However,  such  occurrences  carry  NO
        semantics.  That is, if a local-part has periods within it, an
        address parser will divide the local-part into several tokens,
        but  the  sequence  of  tokens will be treated as one uninter-
        preted unit.  The sequence  will  be  re-assembled,  when  the
        address is passed outside of the system such as to a mail pro-
        tocol service.

        For example, the address:

                           First.Last@Registry.Org

        is legal and does not require the local-part to be  surrounded
        with  quotation-marks.   (However,  "First  Last" DOES require
        quoting.)  The local-part of the address, when passed  outside
        of  the  mail  system,  within  the  Registry.Org  domain,  is
        "First.Last", again without quotation marks.

     6.2.5.  BALANCING LOCAL-PART AND DOMAIN

        In some cases, the boundary between local-part and domain  can
        be  flexible.  The local-part may be a simple string, which is
        used for the final determination of the  recipient's  mailbox.
        All  other  levels  of  reference  are, therefore, part of the
        domain.

        For some systems, in the case of abbreviated reference to  the
        local  and  subordinate  sub-domains,  it  may  be possible to
        specify only one reference within the domain  part  and  place
        the  other,  subordinate  name-domain  references  within  the
        local-part.  This would appear as:

                        mailbox.sub1.sub2@this-domain

        Such a specification would be acceptable  to  address  parsers
        which  conform  to  RFC  #733,  but  do not support this newer
        Internet standard.  While contrary to the intent of this stan-
        dard, the form is legal.

        Also, some sub-domains have a specification syntax which  does
        not conform to this standard.  For example:

                      sub-net.mailbox@sub-domain.domain


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        uses a different parsing  sequence  for  local-part  than  for
        domain.

        Note:  As a rule,  the  domain  specification  should  contain
               fields  which  are  encoded  according to the syntax of
               this standard and which contain  generally-standardized
               information.   The local-part specification should con-
               tain only that portion of the  address  which  deviates
               from the form or intention of the domain field.

     6.2.6.  MULTIPLE MAILBOXES

        An individual may have several mailboxes and wish  to  receive
        mail  at  whatever  mailbox  is  convenient  for the sender to
        access.  This standard does not provide a means of  specifying
        "any member of" a list of mailboxes.

        A set of individuals may wish to receive mail as a single unit
        (i.e.,  a  distribution  list).  The  construct permits
        specification of such a list.  Recipient mailboxes are  speci-
        fied  within  the  bracketed  part (":" - ";").  A copy of the
        transmitted message is to be  sent  to  each  mailbox  listed.
        This  standard  does  not  permit  recursive  specification of
        groups within groups.

        While a list must be named, it is not required that  the  con-
        tents  of  the  list be included.  In this case, the 
serves only as an indication of group distribution and would appear in the form: name:; Some mail services may provide a group-list distribution facility, accepting a single mailbox reference, expanding it to the full distribution list, and relaying the mail to the list's members. This standard provides no additional syntax for indicating such a service. Using the address alternative, while listing one mailbox in it, can mean either that the mailbox reference will be expanded to a list or that there is a group with one member. 6.2.7. EXPLICIT PATH SPECIFICATION At times, a message originator may wish to indicate the transmission path that a message should follow. This is called source routing. The normal addressing scheme, used in an addr-spec, is carefully separated from such information; the portion of a route-addr is provided for such occa- sions. It specifies the sequence of hosts and/or transmission August 13, 1982 - 32 - RFC #822 Standard for ARPA Internet Text Messages services that are to be traversed. Both domain-refs and domain-literals may be used. Note: The use of source routing is discouraged. Unless the sender has special need of path restriction, the choice of transmission route should be left to the mail tran- sport service. 6.3. RESERVED ADDRESS It often is necessary to send mail to a site, without know- ing any of its valid addresses. For example, there may be mail system dysfunctions, or a user may wish to find out a person's correct address, at that site. This standard specifies a single, reserved mailbox address (local-part) which is to be valid at each site. Mail sent to that address is to be routed to a person responsible for the site's mail system or to a person with responsibility for general site operation. The name of the reserved local-part address is: Postmaster so that "Postmaster@domain" is required to be valid. Note: This reserved local-part must be matched without sensi- tivity to alphabetic case, so that "POSTMASTER", "postmas- ter", and even "poStmASteR" is to be accepted. August 13, 1982 - 33 - RFC #822 Standard for ARPA Internet Text Messages 7. BIBLIOGRAPHY ANSI. "USA Standard Code for Information Interchange," X3.4. American National Standards Institute: New York (1968). Also in: Feinler, E. and J. Postel, eds., "ARPANET Protocol Hand- book", NIC 7104. ANSI. "Representations of Universal Time, Local Time Differen- tials, and United States Time Zone References for Information Interchange," X3.51-1975. American National Standards Insti- tute: New York (1975). Bemer, R.W., "Time and the Computer." In: Interface Age (Feb. 1979). Bennett, C.J. "JNT Mail Protocol". Joint Network Team, Ruther- ford and Appleton Laboratory: Didcot, England. Bhushan, A.K., Pogran, K.T., Tomlinson, R.S., and White, J.E. "Standardizing Network Mail Headers," ARPANET Request for Comments No. 561, Network Information Center No. 18516; SRI International: Menlo Park (September 1973). Birrell, A.D., Levin, R., Needham, R.M., and Schroeder, M.D. "Grapevine: An Exercise in Distributed Computing," Communica- tions of the ACM 25, 4 (April 1982), 260-274. Crocker, D.H., Vittal, J.J., Pogran, K.T., Henderson, D.A. "Standard for the Format of ARPA Network Text Message," ARPANET Request for Comments No. 733, Network Information Center No. 41952. SRI International: Menlo Park (November 1977). Feinler, E.J. and Postel, J.B. ARPANET Protocol Handbook, Net- work Information Center No. 7104 (NTIS AD A003890). SRI International: Menlo Park (April 1976). Harary, F. "Graph Theory". Addison-Wesley: Reading, Mass. (1969). Levin, R. and Schroeder, M. "Transport of Electronic Messages through a Network," TeleInformatics 79, pp. 29-33. North Holland (1979). Also as Xerox Palo Alto Research Center Technical Report CSL-79-4. Myer, T.H. and Henderson, D.A. "Message Transmission Protocol," ARPANET Request for Comments, No. 680, Network Information Center No. 32116. SRI International: Menlo Park (1975). August 13, 1982 - 34 - RFC #822 Standard for ARPA Internet Text Messages NBS. "Specification of Message Format for Computer Based Message Systems, Recommended Federal Information Processing Standard." National Bureau of Standards: Gaithersburg, Maryland (October 1981). NIC. Internet Protocol Transition Workbook. Network Information Center, SRI-International, Menlo Park, California (March 1982). Oppen, D.C. and Dalal, Y.K. "The Clearinghouse: A Decentralized Agent for Locating Named Objects in a Distributed Environ- ment," OPD-T8103. Xerox Office Products Division: Palo Alto, CA. (October 1981). Postel, J.B. "Assigned Numbers," ARPANET Request for Comments, No. 820. SRI International: Menlo Park (August 1982). Postel, J.B. "Simple Mail Transfer Protocol," ARPANET Request for Comments, No. 821. SRI International: Menlo Park (August 1982). Shoch, J.F. "Internetwork naming, addressing and routing," in Proc. 17th IEEE Computer Society International Conference, pp. 72-79, Sept. 1978, IEEE Cat. No. 78 CH 1388-8C. Su, Z. and Postel, J. "The Domain Naming Convention for Internet User Applications," ARPANET Request for Comments, No. 819. SRI International: Menlo Park (August 1982). August 13, 1982 - 35 - RFC #822 Standard for ARPA Internet Text Messages APPENDIX A. EXAMPLES A.1. ADDRESSES A.1.1. Alfred Neuman A.1.2. Neuman@BBN-TENEXA These two "Alfred Neuman" examples have identical seman- tics, as far as the operation of the local host's mail sending (distribution) program (also sometimes called its "mailer") and the remote host's mail protocol server are concerned. In the first example, the "Alfred Neuman" is ignored by the mailer, as "Neuman@BBN-TENEXA" completely specifies the reci- pient. The second example contains no superfluous informa- tion, and, again, "Neuman@BBN-TENEXA" is the intended reci- pient. Note: When the message crosses name-domain boundaries, then these specifications must be changed, so as to indicate the remainder of the hierarchy, starting with the top level. A.1.3. "George, Ted" This form might be used to indicate that a single mailbox is shared by several users. The quoted string is ignored by the originating host's mailer, because "Shared@Group.Arpanet" completely specifies the destination mailbox. A.1.4. Wilt . (the Stilt) Chamberlain@NBA.US The "(the Stilt)" is a comment, which is NOT included in the destination mailbox address handed to the originating system's mailer. The local-part of the address is the string "Wilt.Chamberlain", with NO space between the first and second words. A.1.5. Address Lists Gourmets: Pompous Person , Childs@WGBH.Boston, Galloping Gourmet@ ANT.Down-Under (Australian National Television), Cheapie@Discount-Liquors;, Cruisers: Port@Portugal, Jones@SEA;, Another@Somewhere.SomeOrg August 13, 1982 - 36 - RFC #822 Standard for ARPA Internet Text Messages This group list example points out the use of comments and the mixing of addresses and groups. A.2. ORIGINATOR ITEMS A.2.1. Author-sent George Jones logs into his host as "Jones". He sends mail himself. From: Jones@Group.Org or From: George Jones A.2.2. Secretary-sent George Jones logs in as Jones on his host. His secre- tary, who logs in as Secy sends mail for him. Replies to the mail should go to George. From: George Jones Sender: Secy@Other-Group A.2.3. Secretary-sent, for user of shared directory George Jones' secretary sends mail for George. Replies should go to George. From: George Jones Sender: Secy@Other-Group Note that there need not be a space between "Jones" and the "<", but adding a space enhances readability (as is the case in other examples. A.2.4. Committee activity, with one author George is a member of a committee. He wishes to have any replies to his message go to all committee members. From: George Jones Sender: Jones@Host Reply-To: The Committee: Jones@Host.Net, Smith@Other.Org, Doe@Somewhere-Else; Note that if George had not included himself in the August 13, 1982 - 37 - RFC #822 Standard for ARPA Internet Text Messages enumeration of The Committee, he would not have gotten an implicit reply; the presence of the "Reply-to" field SUPER- SEDES the sending of a reply to the person named in the "From" field. A.2.5. Secretary acting as full agent of author George Jones asks his secretary (Secy@Host) to send a message for him in his capacity as Group. He wants his secre- tary to handle all replies. From: George Jones Sender: Secy@Host Reply-To: Secy@Host A.2.6. Agent for user without online mailbox A friend of George's, Sarah, is visiting. George's secretary sends some mail to a friend of Sarah in computer- land. Replies should go to George, whose mailbox is Jones at Registry. From: Sarah Friendly Sender: Secy-Name Reply-To: Jones@Registry. A.2.7. Agent for member of a committee George's secretary sends out a message which was authored jointly by all the members of a committee. Note that the name of the committee cannot be specified, since names are not permitted in the From field. From: Jones@Host, Smith@Other-Host, Doe@Somewhere-Else Sender: Secy@SHost August 13, 1982 - 38 - RFC #822 Standard for ARPA Internet Text Messages A.3. COMPLETE HEADERS A.3.1. Minimum required Date: 26 Aug 76 1429 EDT Date: 26 Aug 76 1429 EDT From: Jones@Registry.Org or From: Jones@Registry.Org Bcc: To: Smith@Registry.Org Note that the "Bcc" field may be empty, while the "To" field is required to have at least one address. A.3.2. Using some of the additional fields Date: 26 Aug 76 1430 EDT From: George Jones Sender: Secy@SHOST To: "Al Neuman"@Mad-Host, Sam.Irving@Other-Host Message-ID: A.3.3. About as complex as you're going to get Date : 27 Aug 76 0932 PDT From : Ken Davis Subject : Re: The Syntax in the RFC Sender : KSecy@Other-Host Reply-To : Sam.Irving@Reg.Organization To : George Jones , Al.Neuman@MAD.Publisher cc : Important folk: Tom Softwood , "Sam Irving"@Other-Host;, Standard Distribution: /main/davis/people/standard@Other-Host, "standard.dist.3"@Tops-20-Host>; Comment : Sam is away on business. He asked me to handle his mail for him. He'll be able to provide a more accurate explanation when he returns next week. In-Reply-To: , George's message X-Special-action: This is a sample of user-defined field- names. There could also be a field-name "Special-action", but its name might later be preempted Message-ID: <4231.629.XYzi-What@Other-Host> August 13, 1982 - 39 - RFC #822 Standard for ARPA Internet Text Messages B. SIMPLE FIELD PARSING Some mail-reading software systems may wish to perform only minimal processing, ignoring the internal syntax of structured field-bodies and treating them the same as unstructured-field- bodies. Such software will need only to distinguish: o Header fields from the message body, o Beginnings of fields from lines which continue fields, o Field-names from field-contents. The abbreviated set of syntactic rules which follows will suffice for this purpose. It describes a limited view of mes- sages and is a subset of the syntactic rules provided in the main part of this specification. One small exception is that the con- tents of field-bodies consist only of text: B.1. SYNTAX message = *field *(CRLF *text) field = field-name ":" [field-body] CRLF field-name = 1* field-body = *text [CRLF LWSP-char field-body] B.2. SEMANTICS Headers occur before the message body and are terminated by a null line (i.e., two contiguous CRLFs). A line which continues a header field begins with a SPACE or HTAB character, while a line beginning a field starts with a printable character which is not a colon. A field-name consists of one or more printable characters (excluding colon, space, and control-characters). A field-name MUST be contained on one line. Upper and lower case are not dis- tinguished when comparing field-names. August 13, 1982 - 40 - RFC #822 Standard for ARPA Internet Text Messages C. DIFFERENCES FROM RFC #733 The following summarizes the differences between this stan- dard and the one specified in Arpanet Request for Comments #733, "Standard for the Format of ARPA Network Text Messages". The differences are listed in the order of their occurrence in the current specification. C.1. FIELD DEFINITIONS C.1.1. FIELD NAMES These now must be a sequence of printable characters. They may not contain any LWSP-chars. C.2. LEXICAL TOKENS C.2.1. SPECIALS The characters period ("."), left-square bracket ("["), and right-square bracket ("]") have been added. For presentation purposes, and when passing a specification to a system that does not conform to this standard, periods are to be contigu- ous with their surrounding lexical tokens. No linear-white- space is permitted between them. The presence of one LWSP- char between other tokens is still directed. C.2.2. ATOM Atoms may not contain SPACE. C.2.3. SPECIAL TEXT ctext and qtext have had backslash ("\") added to the list of prohibited characters. C.2.4. DOMAINS The lexical tokens and have been added. C.3. MESSAGE SPECIFICATION C.3.1. TRACE The "Return-path:" and "Received:" fields have been specified. August 13, 1982 - 41 - RFC #822 Standard for ARPA Internet Text Messages C.3.2. FROM The "From" field must contain machine-usable addresses (addr- spec). Multiple addresses may be specified, but named-lists (groups) may not. C.3.3. RESENT The meta-construct of prefacing field names with the string "Resent-" has been added, to indicate that a message has been forwarded by an intermediate recipient. C.3.4. DESTINATION A message must contain at least one destination address field. "To" and "CC" are required to contain at least one address. C.3.5. IN-REPLY-TO The field-body is no longer a comma-separated list, although a sequence is still permitted. C.3.6. REFERENCE The field-body is no longer a comma-separated list, although a sequence is still permitted. C.3.7. ENCRYPTED A field has been specified that permits senders to indicate that the body of a message has been encrypted. C.3.8. EXTENSION-FIELD Extension fields are prohibited from beginning with the char- acters "X-". C.4. DATE AND TIME SPECIFICATION C.4.1. SIMPLIFICATION Fewer optional forms are permitted and the list of three- letter time zones has been shortened. C.5. ADDRESS SPECIFICATION August 13, 1982 - 42 - RFC #822 Standard for ARPA Internet Text Messages C.5.1. ADDRESS The use of quoted-string, and the ":"-atom-":" construct, have been removed. An address now is either a single mailbox reference or is a named list of addresses. The latter indi- cates a group distribution. C.5.2. GROUPS Group lists are now required to to have a name. Group lists may not be nested. C.5.3. MAILBOX A mailbox specification may indicate a person's name, as before. Such a named list no longer may specify multiple mailboxes and may not be nested. C.5.4. ROUTE ADDRESSING Addresses now are taken to be absolute, global specifications, independent of transmission paths. The construct has been provided, to permit explicit specification of transmis- sion path. RFC #733's use of multiple at-signs ("@") was intended as a general syntax for indicating routing and/or hierarchical addressing. The current standard separates these specifications and only one at-sign is permitted. C.5.5. AT-SIGN The string " at " no longer is used as an address delimiter. Only at-sign ("@") serves the function. C.5.6. DOMAINS Hierarchical, logical name-domains have been added. C.6. RESERVED ADDRESS The local-part "Postmaster" has been reserved, so that users can be guaranteed at least one valid address at a site. August 13, 1982 - 43 - RFC #822 Standard for ARPA Internet Text Messages D. ALPHABETICAL LISTING OF SYNTAX RULES address = mailbox ; one addressee / group ; named list addr-spec = local-part "@" domain ; global address ALPHA = ; (101-132, 65.- 90.) ; (141-172, 97.-122.) atom = 1* authentic = "From" ":" mailbox ; Single author / ( "Sender" ":" mailbox ; Actual submittor "From" ":" 1#mailbox) ; Multiple authors ; or not sender CHAR = ; ( 0-177, 0.-127.) comment = "(" *(ctext / quoted-pair / comment) ")" CR = ; ( 15, 13.) CRLF = CR LF ctext = may be folded ")", "\" & CR, & including linear-white-space> CTL = ; ( 177, 127.) date = 1*2DIGIT month 2DIGIT ; day month year ; e.g. 20 Jun 82 dates = orig-date ; Original [ resent-date ] ; Forwarded date-time = [ day "," ] date time ; dd mm yy ; hh:mm:ss zzz day = "Mon" / "Tue" / "Wed" / "Thu" / "Fri" / "Sat" / "Sun" delimiters = specials / linear-white-space / comment destination = "To" ":" 1#address ; Primary / "Resent-To" ":" 1#address / "cc" ":" 1#address ; Secondary / "Resent-cc" ":" 1#address / "bcc" ":" #address ; Blind carbon / "Resent-bcc" ":" #address DIGIT = ; ( 60- 71, 48.- 57.) domain = sub-domain *("." sub-domain) domain-literal = "[" *(dtext / quoted-pair) "]" domain-ref = atom ; symbolic reference dtext = may be folded "]", "\" & CR, & including linear-white-space> extension-field = August 13, 1982 - 44 - RFC #822 Standard for ARPA Internet Text Messages field = field-name ":" [ field-body ] CRLF fields = dates ; Creation time, source ; author id & one 1*destination ; address required *optional-field ; others optional field-body = field-body-contents [CRLF LWSP-char field-body] field-body-contents = field-name = 1* group = phrase ":" [#mailbox] ";" hour = 2DIGIT ":" 2DIGIT [":" 2DIGIT] ; 00:00:00 - 23:59:59 HTAB = ; ( 11, 9.) LF = ; ( 12, 10.) linear-white-space = 1*([CRLF] LWSP-char) ; semantics = SPACE ; CRLF => folding local-part = word *("." word) ; uninterpreted ; case-preserved LWSP-char = SPACE / HTAB ; semantics = SPACE mailbox = addr-spec ; simple address / phrase route-addr ; name & addr-spec message = fields *( CRLF *text ) ; Everything after ; first null line ; is message body month = "Jan" / "Feb" / "Mar" / "Apr" / "May" / "Jun" / "Jul" / "Aug" / "Sep" / "Oct" / "Nov" / "Dec" msg-id = "<" addr-spec ">" ; Unique message id optional-field = / "Message-ID" ":" msg-id / "Resent-Message-ID" ":" msg-id / "In-Reply-To" ":" *(phrase / msg-id) / "References" ":" *(phrase / msg-id) / "Keywords" ":" #phrase / "Subject" ":" *text / "Comments" ":" *text / "Encrypted" ":" 1#2word / extension-field ; To be defined / user-defined-field ; May be pre-empted orig-date = "Date" ":" date-time originator = authentic ; authenticated addr [ "Reply-To" ":" 1#address] ) phrase = 1*word ; Sequence of words August 13, 1982 - 45 - RFC #822 Standard for ARPA Internet Text Messages qtext = , ; => may be folded "\" & CR, and including linear-white-space> quoted-pair = "\" CHAR ; may quote any char quoted-string = <"> *(qtext/quoted-pair) <">; Regular qtext or ; quoted chars. received = "Received" ":" ; one per relay ["from" domain] ; sending host ["by" domain] ; receiving host ["via" atom] ; physical path *("with" atom) ; link/mail protocol ["id" msg-id] ; receiver msg id ["for" addr-spec] ; initial form ";" date-time ; time received resent = resent-authentic [ "Resent-Reply-To" ":" 1#address] ) resent-authentic = = "Resent-From" ":" mailbox / ( "Resent-Sender" ":" mailbox "Resent-From" ":" 1#mailbox ) resent-date = "Resent-Date" ":" date-time return = "Return-path" ":" route-addr ; return address route = 1#("@" domain) ":" ; path-relative route-addr = "<" [route] addr-spec ">" source = [ trace ] ; net traversals originator ; original mail [ resent ] ; forwarded SPACE = ; ( 40, 32.) specials = "(" / ")" / "<" / ">" / "@" ; Must be in quoted- / "," / ";" / ":" / "\" / <"> ; string, to use / "." / "[" / "]" ; within a word. sub-domain = domain-ref / domain-literal text = atoms, specials, CR & bare LF, but NOT ; comments and including CRLF> ; quoted-strings are ; NOT recognized. time = hour zone ; ANSI and Military trace = return ; path to sender 1*received ; receipt tags user-defined-field = word = atom / quoted-string August 13, 1982 - 46 - RFC #822 Standard for ARPA Internet Text Messages zone = "UT" / "GMT" ; Universal Time ; North American : UT / "EST" / "EDT" ; Eastern: - 5/ - 4 / "CST" / "CDT" ; Central: - 6/ - 5 / "MST" / "MDT" ; Mountain: - 7/ - 6 / "PST" / "PDT" ; Pacific: - 8/ - 7 / 1ALPHA ; Military: Z = UT; <"> = ; ( 42, 34.) August 13, 1982 - 47 - RFC #822