                       Internet RFC/STD/FYI/BCP Archives

                                     RFC822

               [ Index | Search | What's New | Comments | Help ]

     ----------------------------------------------------------------------


      RFC #  822

      Obsoletes:  RFC #733  (NIC #41952)

                         STANDARD FOR THE FORMAT OF

                         ARPA INTERNET TEXT MESSAGES

                               August 13, 1982

                                 Revised by

                              David H. Crocker

                       Dept. of Electrical Engineering
                  University of Delaware, Newark, DE  19711
                       Network:  DCrocker @ UDel-Relay

      Standard for ARPA Internet Text Messages

                              TABLE OF CONTENTS

      PREFACE ....................................................   ii

      1.  INTRODUCTION ...........................................    1

          1.1.  Scope ............................................    1
          1.2.  Communication Framework ..........................    2

      2.  NOTATIONAL CONVENTIONS .................................    3

      3.  LEXICAL ANALYSIS OF MESSAGES ...........................    5

          3.1.  General Description ..............................    5
          3.2.  Header Field Definitions .........................    9
          3.3.  Lexical Tokens ...................................   10
          3.4.  Clarifications ...................................   11

      4.  MESSAGE SPECIFICATION ..................................   17

          4.1.  Syntax ...........................................   17
          4.2.  Forwarding .......................................   19
          4.3.  Trace Fields .....................................   20
          4.4.  Originator Fields ................................   21
          4.5.  Receiver Fields ..................................   23
          4.6.  Reference Fields .................................   23
          4.7.  Other Fields .....................................   24

      5.  DATE AND TIME SPECIFICATION ............................   26

          5.1.  Syntax ...........................................   26
          5.2.  Semantics ........................................   26

      6.  ADDRESS SPECIFICATION ..................................   27

          6.1.  Syntax ...........................................   27
          6.2.  Semantics ........................................   27
          6.3.  Reserved Address .................................   33

      7.  BIBLIOGRAPHY ...........................................   34

                              APPENDIX

      A.  EXAMPLES ...............................................   36
      B.  SIMPLE FIELD PARSING ...................................   40
      C.  DIFFERENCES FROM RFC #733 ..............................   41
      D.  ALPHABETICAL LISTING OF SYNTAX RULES ...................   44

      August 13, 1982               - i -                      RFC #822

      Standard for ARPA Internet Text Messages

                                   PREFACE

           By 1977, the Arpanet employed several informal standards for
      the  text  messages (mail) sent among its host computers.  It was
      felt necessary to codify these practices and  provide  for  those
      features  that  seemed  imminent.   The result of that effort was
      Request for Comments (RFC) #733, "Standard for the Format of ARPA
      Network Text Message", by Crocker, Vittal, Pogran, and Henderson.
      The specification attempted to avoid major  changes  in  existing
      software, while permitting several new features.

           This document revises the specifications  in  RFC  #733,  in
      order  to  serve  the  needs  of the larger and more complex ARPA
      Internet.  Some of RFC #733's features failed  to  gain  adequate
      acceptance.   In  order to simplify the standard and the software
      that follows it, these features have been removed.   A  different
      addressing  scheme  is  used, to handle the case of inter-network
      mail; and the concept of re-transmission has been introduced.

           This specification is intended for use in the ARPA Internet.
      However, an attempt has been made to free it of any dependence on
      that environment, so that it can be applied to other network text
      message systems.

           The specification of RFC #733 took place over the course  of
      one  year, using the ARPANET mail environment, itself, to provide
      an on-going forum for discussing the capabilities to be included.
      More  than  twenty individuals, from across the country, partici-
      pated in  the  original  discussion.   The  development  of  this
      revised specification has, similarly, utilized network mail-based
      group discussion.  Both specification efforts  greatly  benefited
      from the comments and ideas of the participants.

           The syntax of the standard,  in  RFC  #733,  was  originally
      specified  in  the  Backus-Naur Form (BNF) meta-language.  Ken L.
      Harrenstien, of SRI International, was responsible for  re-coding
      the  BNF  into  an  augmented  BNF  that makes the representation
      smaller and easier to understand.

      August 13, 1982              - ii -                      RFC #822

      Standard for ARPA Internet Text Messages

      1.  INTRODUCTION

      1.1.  SCOPE

           This standard specifies a syntax for text messages that  are
      sent  among  computer  users, within the framework of "electronic
      mail".  The standard supersedes  the  one  specified  in  ARPANET
      Request  for Comments #733, "Standard for the Format of ARPA Net-
      work Text Messages".

           In this context, messages are viewed as having  an  envelope
      and  contents.   The  envelope  contains  whatever information is
      needed to accomplish transmission  and  delivery.   The  contents
      compose  the object to be delivered to the recipient.  This stan-
      dard applies only to the format and some of the semantics of mes-
      sage  contents.   It contains no specification of the information
      in the envelope.

           However, some message systems may use information  from  the
      contents  to create the envelope.  It is intended that this stan-
      dard facilitate the acquisition of such information by programs.

           Some message systems may  store  messages  in  formats  that
      differ  from the one specified in this standard.  This specifica-
      tion is intended strictly as a definition of what message content
      format is to be passed BETWEEN hosts.

      Note:  This standard is NOT intended to dictate the internal for-
             mats  used  by sites, the specific message system features
             that they are expected to support, or any of  the  charac-
             teristics  of  user interface programs that create or read
             messages.

           A distinction should be made between what the  specification
      REQUIRES  and  what  it ALLOWS.  Messages can be made complex and
      rich with formally-structured components of information or can be
      kept small and simple, with a minimum of such information.  Also,
      the standard simplifies the interpretation  of  differing  visual
      formats  in  messages;  only  the  visual  aspect of a message is
      affected and not the interpretation  of  information  within  it.
      Implementors may choose to retain such visual distinctions.

           The formal definition is divided into four levels.  The bot-
      tom level describes the meta-notation used in this document.  The
      second level describes basic lexical analyzers that  feed  tokens
      to  higher-level  parsers.   Next is an overall specification for
      messages; it permits distinguishing individual fields.   Finally,
      there is definition of the contents of several structured fields.

      August 13, 1982               - 1 -                      RFC #822

      Standard for ARPA Internet Text Messages

      1.2.  COMMUNICATION FRAMEWORK

           Messages consist of lines of text.   No  special  provisions
      are  made for encoding drawings, facsimile, speech, or structured
      text.  No significant consideration has been given  to  questions
      of  data  compression  or to transmission and storage efficiency,
      and the standard tends to be free with the number  of  bits  con-
      sumed.   For  example,  field  names  are specified as free text,
      rather than special terse codes.

           A general "memo" framework is used.  That is, a message con-
      sists of some information in a rigid format, followed by the main
      part of the message, with a format that is not specified in  this
      document.   The  syntax of several fields of the rigidly-formated
      ("headers") section is defined in  this  specification;  some  of
      these fields must be included in all messages.

           The syntax  that  distinguishes  between  header  fields  is
      specified  separately  from  the  internal  syntax for particular
      fields.  This separation is intended to allow simple  parsers  to
      operate on the general structure of messages, without concern for
      the detailed structure of individual header fields.   Appendix  B
      is provided to facilitate construction of these parsers.

           In addition to the fields specified in this document, it  is
      expected  that  other fields will gain common use.  As necessary,
      the specifications for these "extension-fields" will be published
      through  the same mechanism used to publish this document.  Users
      may also  wish  to  extend  the  set  of  fields  that  they  use
      privately.  Such "user-defined fields" are permitted.

           The framework severely constrains document tone and  appear-
      ance and is primarily useful for most intra-organization communi-
      cations and  well-structured   inter-organization  communication.
      It  also  can  be used for some types of inter-process communica-
      tion, such as simple file transfer and remote job entry.  A  more
      robust  framework might allow for multi-font, multi-color, multi-
      dimension encoding of information.  A  less  robust  one,  as  is
      present  in  most  single-machine  message  systems,  would  more
      severely constrain the ability to add fields and the decision  to
      include specific fields.  In contrast with paper-based communica-
      tion, it is interesting to note that the RECEIVER  of  a  message
      can   exercise  an  extraordinary  amount  of  control  over  the
      message's appearance.  The amount of actual control available  to
      message  receivers  is  contingent upon the capabilities of their
      individual message systems.

      August 13, 1982               - 2 -                      RFC #822

      Standard for ARPA Internet Text Messages

      2.  NOTATIONAL CONVENTIONS

           This specification uses an augmented Backus-Naur Form  (BNF)
      notation.  The differences from standard BNF involve naming rules
      and indicating repetition and "local" alternatives.

      2.1.  RULE NAMING

           Angle brackets ("<", ">") are not  used,  in  general.   The
      name  of  a rule is simply the name itself, rather than "<name>".
      Quotation-marks enclose literal text (which may be  upper  and/or
      lower  case).   Certain  basic  rules  are  in uppercase, such as
      SPACE, TAB, CRLF, DIGIT, ALPHA, etc.  Angle brackets are used  in
      rule  definitions,  and  in  the rest of this  document, whenever
      their presence will facilitate discerning the use of rule names.

      2.2.  RULE1 / RULE2:  ALTERNATIVES

           Elements separated by slash ("/") are alternatives.   There-
      fore "foo / bar" will accept foo or bar.

      2.3.  (RULE1 RULE2):  LOCAL ALTERNATIVES

           Elements enclosed in parentheses are  treated  as  a  single
      element.   Thus,  "(elem  (foo  /  bar)  elem)"  allows the token
      sequences "elem foo elem" and "elem bar elem".

      2.4.  *RULE:  REPETITION

           The character "*" preceding an element indicates repetition.
      The full form is:

                               <l>*<m>element

      indicating at least <l> and at most <m> occurrences  of  element.
      Default values are 0 and infinity so that "*(element)" allows any
      number, including zero; "1*element" requires at  least  one;  and
      "1*2element" allows one or two.

      2.5.  [RULE]:  OPTIONAL

           Square brackets enclose optional elements; "[foo  bar]"   is
      equivalent to "*1(foo bar)".

      2.6.  NRULE:  SPECIFIC REPETITION

           "<n>(element)" is equivalent to "<n>*<n>(element)"; that is,
      exactly  <n>  occurrences  of (element). Thus 2DIGIT is a 2-digit
      number, and 3ALPHA is a string of three alphabetic characters.

      August 13, 1982               - 3 -                      RFC #822

      Standard for ARPA Internet Text Messages

      2.7.  #RULE:  LISTS

           A construct "#" is defined, similar to "*", as follows:

                               <l>#<m>element

      indicating at least <l> and at most <m> elements, each  separated
      by  one  or more commas (","). This makes the usual form of lists
      very easy; a rule such as '(element *("," element))' can be shown
      as  "1#element".   Wherever this construct is used, null elements
      are allowed, but do not  contribute  to  the  count  of  elements
      present.   That  is,  "(element),,(element)"  is  permitted,  but
      counts as only two elements.  Therefore, where at least one  ele-
      ment  is required, at least one non-null element must be present.
      Default values are 0 and infinity so that "#(element)" allows any
      number,  including  zero;  "1#element" requires at least one; and
      "1#2element" allows one or two.

      2.8.  ; COMMENTS

           A semi-colon, set off some distance to  the  right  of  rule
      text,  starts  a comment that continues to the end of line.  This
      is a simple way of including useful notes in  parallel  with  the
      specifications.

      August 13, 1982               - 4 -                      RFC #822

      Standard for ARPA Internet Text Messages

      3.  LEXICAL ANALYSIS OF MESSAGES

      3.1.  GENERAL DESCRIPTION

           A message consists of header fields and, optionally, a body.
      The  body  is simply a sequence of lines containing ASCII charac-
      ters.  It is separated from the headers by a null line  (i.e.,  a
      line with nothing preceding the CRLF).

      3.1.1.  LONG HEADER FIELDS

         Each header field can be viewed as a single, logical  line  of
         ASCII  characters,  comprising  a field-name and a field-body.
         For convenience, the field-body  portion  of  this  conceptual
         entity  can be split into a multiple-line representation; this
         is called "folding".  The general rule is that wherever  there
         may  be  linear-white-space  (NOT  simply  LWSP-chars), a CRLF
         immediately followed by AT LEAST one LWSP-char may instead  be
         inserted.  Thus, the single line

             To:  "Joe & J. Harvey" <ddd @Org>, JJV @ BBN

         can be represented as:

             To:  "Joe & J. Harvey" <ddd @ Org>,
                     JJV@BBN

         and

             To:  "Joe & J. Harvey"
                             <ddd@ Org>, JJV
              @BBN

         and

             To:  "Joe &
              J. Harvey" <ddd @ Org>, JJV @ BBN

              The process of moving  from  this  folded   multiple-line
         representation  of a header field to its single line represen-
         tation is called "unfolding".  Unfolding  is  accomplished  by
         regarding   CRLF   immediately  followed  by  a  LWSP-char  as
         equivalent to the LWSP-char.

         Note:  While the standard  permits  folding  wherever  linear-
                white-space is permitted, it is recommended that struc-
                tured fields, such as those containing addresses, limit
                folding  to higher-level syntactic breaks.  For address
                fields, it  is  recommended  that  such  folding  occur

      August 13, 1982               - 5 -                      RFC #822

      Standard for ARPA Internet Text Messages

                between addresses, after the separating comma.

      3.1.2.  STRUCTURE OF HEADER FIELDS

         Once a field has been unfolded, it may be viewed as being com-
         posed of a field-name followed by a colon (":"), followed by a
         field-body, and  terminated  by  a  carriage-return/line-feed.
         The  field-name must be composed of printable ASCII characters
         (i.e., characters that  have  values  between  33.  and  126.,
         decimal, except colon).  The field-body may be composed of any
         ASCII characters, except CR or LF.  (While CR and/or LF may be
         present  in the actual text, they are removed by the action of
         unfolding the field.)

         Certain field-bodies of headers may be  interpreted  according
         to  an  internal  syntax  that some systems may wish to parse.
         These  fields  are  called  "structured   fields".    Examples
         include  fields containing dates and addresses.  Other fields,
         such as "Subject"  and  "Comments",  are  regarded  simply  as
         strings of text.

         Note:  Any field which has a field-body  that  is  defined  as
                other  than  simply <text> is to be treated as a struc-
                tured field.

                Field-names, unstructured field bodies  and  structured
                field bodies each are scanned by their own, independent
                "lexical" analyzers.

      3.1.3.  UNSTRUCTURED FIELD BODIES

         For some fields, such as "Subject" and "Comments",  no  struc-
         turing  is assumed, and they are treated simply as <text>s, as
         in the message body.  Rules of folding apply to these  fields,
         so  that  such  field  bodies  which occupy several lines must
         therefore have the second and successive lines indented by  at
         least one LWSP-char.

      3.1.4.  STRUCTURED FIELD BODIES

         To aid in the creation and reading of structured  fields,  the
         free  insertion   of linear-white-space (which permits folding
         by inclusion of CRLFs)  is  allowed  between  lexical  tokens.
         Rather  than  obscuring  the  syntax  specifications for these
         structured fields with explicit syntax for this  linear-white-
         space, the existence of another "lexical" analyzer is assumed.
         This analyzer does not apply  for  unstructured  field  bodies
         that  are  simply  strings  of  text, as described above.  The
         analyzer provides  an  interpretation  of  the  unfolded  text

      August 13, 1982               - 6 -                      RFC #822

      Standard for ARPA Internet Text Messages

         composing  the body of the field as a sequence of lexical sym-
         bols.

         These symbols are:

                      -  individual special characters
                      -  quoted-strings
                      -  domain-literals
                      -  comments
                      -  atoms

         The first four of these symbols  are  self-delimiting.   Atoms
         are not; they are delimited by the self-delimiting symbols and
         by  linear-white-space.   For  the  purposes  of  regenerating
         sequences  of  atoms  and quoted-strings, exactly one SPACE is
         assumed to exist, and should be used, between them.  (Also, in
         the "Clarifications" section on "White Space", below, note the
         rules about treatment of multiple contiguous LWSP-chars.)

         So, for example, the folded body of an address field

             ":sysmail"@  Some-Group. Some-Org,
             Muhammed.(I am  the greatest) Ali @(the)Vegas.WBA

      August 13, 1982               - 7 -                      RFC #822

      Standard for ARPA Internet Text Messages

         is analyzed into the following lexical symbols and types:

                     :sysmail              quoted string
                     @                     special
                     Some-Group            atom
                     .                     special
                     Some-Org              atom
                     ,                     special
                     Muhammed              atom
                     .                     special
                     (I am  the greatest)  comment
                     Ali                   atom
                     @                     atom
                     (the)                 comment
                     Vegas                 atom
                     .                     special
                     WBA                   atom

         The canonical representations for the data in these  addresses
         are the following strings:

                         ":sysmail"@Some-Group.Some-Org

         and

                             Muhammed.Ali@Vegas.WBA

         Note:  For purposes of display, and when passing  such  struc-
                tured information to other systems, such as mail proto-
                col  services,  there  must  be  NO  linear-white-space
                between  <word>s  that are separated by period (".") or
                at-sign ("@") and exactly one SPACE between  all  other
                <word>s.  Also, headers should be in a folded form.

      August 13, 1982               - 8 -                      RFC #822

      Standard for ARPA Internet Text Messages

      3.2.  HEADER FIELD DEFINITIONS

           These rules show a field meta-syntax, without regard for the
      particular  type  or internal syntax.  Their purpose is to permit
      detection of fields; also, they present to  higher-level  parsers
      an image of each field as fitting on one line.

      field       =  field-name ":" [ field-body ] CRLF

      field-name  =  1*<any CHAR, excluding CTLs, SPACE, and ":">

      field-body  =  field-body-contents
                     [CRLF LWSP-char field-body]

      field-body-contents =
                    <the ASCII characters making up the field-body, as
                     defined in the following sections, and consisting
                     of combinations of atom, quoted-string, and
                     specials tokens, or else consisting of texts>

      August 13, 1982               - 9 -                      RFC #822

      Standard for ARPA Internet Text Messages

      3.3.  LEXICAL TOKENS

           The following rules are used to define an underlying lexical
      analyzer,  which  feeds  tokens to higher level parsers.  See the
      ANSI references, in the Bibliography.

                                                  ; (  Octal, Decimal.)
      CHAR        =  <any ASCII character>        ; (  0-177,  0.-127.)
      ALPHA       =  <any ASCII alphabetic character>
                                                  ; (101-132, 65.- 90.)
                                                  ; (141-172, 97.-122.)
      DIGIT       =  <any ASCII decimal digit>    ; ( 60- 71, 48.- 57.)
      CTL         =  <any ASCII control           ; (  0- 37,  0.- 31.)
                      character and DEL>          ; (    177,     127.)
      CR          =  <ASCII CR, carriage return>  ; (     15,      13.)
      LF          =  <ASCII LF, linefeed>         ; (     12,      10.)
      SPACE       =  <ASCII SP, space>            ; (     40,      32.)
      HTAB        =  <ASCII HT, horizontal-tab>   ; (     11,       9.)
      <">         =  <ASCII quote mark>           ; (     42,      34.)
      CRLF        =  CR LF

      LWSP-char   =  SPACE / HTAB                 ; semantics = SPACE

      linear-white-space =  1*([CRLF] LWSP-char)  ; semantics = SPACE
                                                  ; CRLF => folding

      specials    =  "(" / ")" / "<" / ">" / "@"  ; Must be in quoted-
                  /  "," / ";" / ":" / "\" / <">  ;  string, to use
                  /  "." / "[" / "]"              ;  within a word.

      delimiters  =  specials / linear-white-space / comment

      text        =  <any CHAR, including bare    ; => atoms, specials,
                      CR & bare LF, but NOT       ;  comments and
                      including CRLF>             ;  quoted-strings are
                                                  ;  NOT recognized.

      atom        =  1*<any CHAR except specials, SPACE and CTLs>

      quoted-string = <"> *(qtext/quoted-pair) <">; Regular qtext or
                                                  ;   quoted chars.

      qtext       =  <any CHAR excepting <">,     ; => may be folded
                      "\" & CR, and including
                      linear-white-space>

      domain-literal =  "[" *(dtext / quoted-pair) "]"

      August 13, 1982              - 10 -                      RFC #822

      Standard for ARPA Internet Text Messages

      dtext       =  <any CHAR excluding "[",     ; => may be folded
                      "]", "\" & CR, & including
                      linear-white-space>

      comment     =  "(" *(ctext / quoted-pair / comment) ")"

      ctext       =  <any CHAR excluding "(",     ; => may be folded
                      ")", "\" & CR, & including
                      linear-white-space>

      quoted-pair =  "\" CHAR                     ; may quote any char

      phrase      =  1*word                       ; Sequence of words

      word        =  atom / quoted-string

      3.4.  CLARIFICATIONS

      3.4.1.  QUOTING

         Some characters are reserved for special interpretation,  such
         as  delimiting lexical tokens.  To permit use of these charac-
         ters as uninterpreted data, a quoting mechanism  is  provided.
         To quote a character, precede it with a backslash ("\").

         This mechanism is not fully general.  Characters may be quoted
         only  within  a subset of the lexical constructs.  In particu-
         lar, quoting is limited to use within:

                              -  quoted-string
                              -  domain-literal
                              -  comment

         Within these constructs, quoting is REQUIRED for  CR  and  "\"
         and for the character(s) that delimit the token (e.g., "(" and
         ")" for a comment).  However, quoting  is  PERMITTED  for  any
         character.

         Note:  In particular, quoting is NOT permitted  within  atoms.
                For  example  when  the local-part of an addr-spec must
                contain a special character, a quoted  string  must  be
                used.  Therefore, a specification such as:

                             Full\ Name@Domain

                is not legal and must be specified as:

                             "Full Name"@Domain

      August 13, 1982              - 11 -                      RFC #822

      Standard for ARPA Internet Text Messages

      3.4.2.  WHITE SPACE

         Note:  In structured field bodies, multiple linear space ASCII
                characters  (namely  HTABs  and  SPACEs) are treated as
                single spaces and may freely surround any  symbol.   In
                all header fields, the only place in which at least one
                LWSP-char is REQUIRED is at the beginning of  continua-
                tion lines in a folded field.

         When passing text to processes  that  do  not  interpret  text
         according to this standard (e.g., mail protocol servers), then
         NO linear-white-space characters should occur between a period
         (".") or at-sign ("@") and a <word>.  Exactly ONE SPACE should
         be used in place of arbitrary linear-white-space  and  comment
         sequences.

         Note:  Within systems conforming to this standard, wherever  a
                member of the list of delimiters is allowed, LWSP-chars
                may also occur before and/or after it.

         Writers of  mail-sending  (i.e.,  header-generating)  programs
         should realize that there is no network-wide definition of the
         effect of ASCII HT (horizontal-tab) characters on the  appear-
         ance  of  text  at another network host; therefore, the use of
         tabs in message headers, though permitted, is discouraged.

      3.4.3.  COMMENTS

         A comment is a set of ASCII characters, which is  enclosed  in
         matching  parentheses  and which is not within a quoted-string
         The comment construct permits message originators to add  text
         which  will  be  useful  for  human readers, but which will be
         ignored by the formal semantics.  Comments should be  retained
         while  the  message  is subject to interpretation according to
         this standard.  However, comments  must  NOT  be  included  in
         other  cases,  such  as  during  protocol  exchanges with mail
         servers.

         Comments nest, so that if an unquoted left parenthesis  occurs
         in  a  comment  string,  there  must  also be a matching right
         parenthesis.  When a comment acts as the delimiter  between  a
         sequence of two lexical symbols, such as two atoms, it is lex-
         ically equivalent with a single SPACE,  for  the  purposes  of
         regenerating  the  sequence, such as when passing the sequence
         onto a mail protocol server.  Comments are  detected  as  such
         only within field-bodies of structured fields.

         If a comment is to be "folded" onto multiple lines,  then  the
         syntax  for  folding  must  be  adhered to.  (See the "Lexical

      August 13, 1982              - 12 -                      RFC #822

      Standard for ARPA Internet Text Messages

         Analysis of Messages" section on "Folding Long Header  Fields"
         above,  and  the  section on "Case Independence" below.)  Note
         that  the  official  semantics  therefore  do  not  "see"  any
         unquoted CRLFs that are in comments, although particular pars-
         ing programs may wish to note their presence.  For these  pro-
         grams,  it would be reasonable to interpret a "CRLF LWSP-char"
         as being a CRLF that is part of the comment; i.e., the CRLF is
         kept  and  the  LWSP-char is discarded.  Quoted CRLFs (i.e., a
         backslash followed by a CR followed by a  LF)  still  must  be
         followed by at least one LWSP-char.

      3.4.4.  DELIMITING AND QUOTING CHARACTERS

         The quote character (backslash) and  characters  that  delimit
         syntactic  units  are not, generally, to be taken as data that
         are part of the delimited or quoted unit(s).   In  particular,
         the   quotation-marks   that   define   a  quoted-string,  the
         parentheses that define  a  comment  and  the  backslash  that
         quotes  a  following  character  are  NOT  part of the quoted-
         string, comment or quoted character.  A quotation-mark that is
         to  be  part  of  a quoted-string, a parenthesis that is to be
         part of a comment and a backslash that is to be part of either
         must  each be preceded by the quote-character backslash ("\").
         Note that the syntax allows any character to be quoted  within
         a  quoted-string  or  comment; however only certain characters
         MUST be quoted to be included as data.  These  characters  are
         the  ones that are not part of the alternate text group (i.e.,
         ctext or qtext).

         The one exception to this rule  is  that  a  single  SPACE  is
         assumed  to  exist  between  contiguous words in a phrase, and
         this interpretation is independent of  the  actual  number  of
         LWSP-chars  that  the  creator  places  between the words.  To
         include more than one SPACE, the creator must make  the  LWSP-
         chars be part of a quoted-string.

         Quotation marks that delimit a quoted string  and  backslashes
         that  quote  the  following character should NOT accompany the
         quoted-string when the string is passed to processes  that  do
         not interpret data according to this specification (e.g., mail
         protocol servers).

      3.4.5.  QUOTED-STRINGS

         Where permitted (i.e., in words in structured fields)  quoted-
         strings  are  treated  as a single symbol.  That is, a quoted-
         string is equivalent to an atom, syntactically.  If a  quoted-
         string  is to be "folded" onto multiple lines, then the syntax
         for folding must be adhered to.  (See the "Lexical Analysis of

      August 13, 1982              - 13 -                      RFC #822

      Standard for ARPA Internet Text Messages

         Messages"  section  on "Folding Long Header Fields" above, and
         the section on "Case  Independence"  below.)   Therefore,  the
         official  semantics  do  not  "see" any bare CRLFs that are in
         quoted-strings; however particular parsing programs  may  wish
         to  note  their presence.  For such programs, it would be rea-
         sonable to interpret a "CRLF LWSP-char" as being a CRLF  which
         is  part  of the quoted-string; i.e., the CRLF is kept and the
         LWSP-char is discarded.  Quoted CRLFs (i.e., a backslash  fol-
         lowed  by  a CR followed by a LF) are also subject to rules of
         folding, but the presence of the quoting character (backslash)
         explicitly  indicates  that  the  CRLF  is  data to the quoted
         string.  Stripping off the first following LWSP-char  is  also
         appropriate when parsing quoted CRLFs.

      3.4.6.  BRACKETING CHARACTERS

         There is one type of bracket which must occur in matched pairs
         and may have pairs nested within each other:

             o   Parentheses ("(" and ")") are used  to  indicate  com-
                 ments.

         There are three types of brackets which must occur in  matched
         pairs, and which may NOT be nested:

             o   Colon/semi-colon (":" and ";") are   used  in  address
                 specifications  to  indicate that the included list of
                 addresses are to be treated as a group.

             o   Angle brackets ("<" and ">")  are  generally  used  to
                 indicate  the  presence of a one machine-usable refer-
                 ence (e.g., delimiting mailboxes), possibly  including
                 source-routing to the machine.

             o   Square brackets ("[" and "]") are used to indicate the
                 presence  of  a  domain-literal, which the appropriate
                 name-domain  is  to  use  directly,  bypassing  normal
                 name-resolution mechanisms.

      3.4.7.  CASE INDEPENDENCE

         Except as noted, alphabetic strings may be represented in  any
         combination of upper and lower case.  The only syntactic units

      August 13, 1982              - 14 -                      RFC #822

      Standard for ARPA Internet Text Messages

         which requires preservation of case information are:

                     -  text
                     -  qtext
                     -  dtext
                     -  ctext
                     -  quoted-pair
                     -  local-part, except "Postmaster"

         When matching any other syntactic unit, case is to be ignored.
         For  example, the field-names "From", "FROM", "from", and even
         "FroM" are semantically equal and should all be treated ident-
         ically.

         When generating these units, any mix of upper and  lower  case
         alphabetic  characters  may  be  used.  The case shown in this
         specification is suggested for message-creating processes.

         Note:  The reserved local-part address unit, "Postmaster",  is
                an  exception.   When  the  value "Postmaster" is being
                interpreted, it must be  accepted  in  any  mixture  of
                case, including "POSTMASTER", and "postmaster".

      3.4.8.  FOLDING LONG HEADER FIELDS

         Each header field may be represented on exactly one line  con-
         sisting  of the name of the field and its body, and terminated
         by a CRLF; this is what the parser sees.  For readability, the
         field-body  portion of long header fields may be "folded" onto
         multiple lines of the actual field.  "Long" is commonly inter-
         preted  to  mean greater than 65 or 72 characters.  The former
         length serves as a limit, when the message is to be viewed  on
         most  simple terminals which use simple display software; how-
         ever, the limit is not imposed by this standard.

         Note:  Some display software often can selectively fold lines,
                to  suit  the display terminal.  In such cases, sender-
                provided  folding  can  interfere  with   the   display
                software.

      3.4.9.  BACKSPACE CHARACTERS

         ASCII BS characters (Backspace, decimal 8) may be included  in
         texts and quoted-strings to effect overstriking.  However, any
         use of backspaces which effects an overstrike to the  left  of
         the beginning of the text or quoted-string is prohibited.

      August 13, 1982              - 15 -                      RFC #822

      Standard for ARPA Internet Text Messages

      3.4.10.  NETWORK-SPECIFIC TRANSFORMATIONS

         During transmission through heterogeneous networks, it may  be
         necessary  to  force data to conform to a network's local con-
         ventions.  For example, it may be required that a CR  be  fol-
         lowed  either by LF, making a CRLF, or by <null>, if the CR is
         to stand alone).  Such transformations are reversed, when  the
         message exits that network.

         When  crossing  network  boundaries,  the  message  should  be
         treated  as  passing  through  two modules.  It will enter the
         first module containing whatever network-specific  transforma-
         tions  that  were  necessary  to  permit migration through the
         "current" network.  It then passes through the modules:

             o   Transformation Reversal

                 The "current" network's idiosyncracies are removed and
                 the  message  is returned to the canonical form speci-
                 fied in this standard.

             o   Transformation

                 The "next" network's local idiosyncracies are  imposed
                 on the message.

                                 ------------------
                     From   ==>  | Remove Net-A   |
                     Net-A       | idiosyncracies |
                                 ------------------
                                        ||
                                        \/
                                   Conformance
                                   with standard
                                        ||
                                        \/
                                 ------------------
                                 | Impose Net-B   |  ==>  To
                                 | idiosyncracies |       Net-B
                                 ------------------

      August 13, 1982              - 16 -                      RFC #822

      Standard for ARPA Internet Text Messages

      4.  MESSAGE SPECIFICATION

      4.1.  SYNTAX

      Note:  Due to an artifact of the notational conventions, the syn-
             tax  indicates that, when present, some fields, must be in
             a particular order.  Header fields  are  NOT  required  to
             occur  in  any  particular  order, except that the message
             body must occur AFTER  the  headers.   It  is  recommended
             that,  if  present,  headers be sent in the order "Return-
             Path", "Received", "Date",  "From",  "Subject",  "Sender",
             "To", "cc", etc.

             This specification permits multiple  occurrences  of  most
             fields.   Except  as  noted,  their  interpretation is not
             specified here, and their use is discouraged.

           The following syntax for the bodies of various fields should
      be  thought  of  as  describing  each field body as a single long
      string (or line).  The "Lexical Analysis of Message"  section  on
      "Long  Header Fields", above, indicates how such long strings can
      be represented on more than one line in  the  actual  transmitted
      message.

      message     =  fields *( CRLF *text )       ; Everything after
                                                  ;  first null line
                                                  ;  is message body

      fields      =    dates                      ; Creation time,
                       source                     ;  author id & one
                     1*destination                ;  address required
                      *optional-field             ;  others optional

      source      = [  trace ]                    ; net traversals
                       originator                 ; original mail
                    [  resent ]                   ; forwarded

      trace       =    return                     ; path to sender
                     1*received                   ; receipt tags

      return      =  "Return-path" ":" route-addr ; return address

      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

      August 13, 1982              - 17 -                      RFC #822

      Standard for ARPA Internet Text Messages

                         ";"    date-time         ; time received

      originator  =   authentic                   ; authenticated addr
                    [ "Reply-To"   ":" 1#address] )

      authentic   =   "From"       ":"   mailbox  ; Single author
                  / ( "Sender"     ":"   mailbox  ; Actual submittor
                      "From"       ":" 1#mailbox) ; Multiple authors
                                                  ;  or not sender

      resent      =   resent-authentic
                    [ "Resent-Reply-To"  ":" 1#address] )

      resent-authentic =
                  =   "Resent-From"      ":"   mailbox
                  / ( "Resent-Sender"    ":"   mailbox
                      "Resent-From"      ":" 1#mailbox  )

      dates       =   orig-date                   ; Original
                    [ resent-date ]               ; Forwarded

      orig-date   =  "Date"        ":"   date-time

      resent-date =  "Resent-Date" ":"   date-time

      destination =  "To"          ":" 1#address  ; Primary
                  /  "Resent-To"   ":" 1#address
                  /  "cc"          ":" 1#address  ; Secondary
                  /  "Resent-cc"   ":" 1#address
                  /  "bcc"         ":"  #address  ; Blind carbon
                  /  "Resent-bcc"  ":"  #address

      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

      msg-id      =  "<" addr-spec ">"            ; Unique message id

      August 13, 1982              - 18 -                      RFC #822

      Standard for ARPA Internet Text Messages

      extension-field =
                    <Any field which is defined in a document
                     published as a formal extension to this
                     specification; none will have names beginning
                     with the string "X-">

      user-defined-field =
                    <Any field which has not been defined
                     in this specification or published as an
                     extension to this specification; names for
                     such fields must be unique and may be
                     pre-empted by published extensions>

      4.2.  FORWARDING

           Some systems permit mail recipients to  forward  a  message,
      retaining  the original headers, by adding some new fields.  This
      standard supports such a service, through the "Resent-" prefix to
      field names.

           Whenever the string "Resent-" begins a field name, the field
      has  the  same  semantics as a field whose name does not have the
      prefix.  However, the message is assumed to have  been  forwarded
      by  an original recipient who attached the "Resent-" field.  This
      new field is treated as being more recent  than  the  equivalent,
      original  field.   For  example, the "Resent-From", indicates the
      person that forwarded the message, whereas the "From" field indi-
      cates the original author.

           Use of such precedence  information  depends  upon  partici-
      pants'  communication needs.  For example, this standard does not
      dictate when a "Resent-From:" address should receive replies,  in
      lieu of sending them to the "From:" address.

      Note:  In general, the "Resent-" fields should be treated as con-
             taining  a  set  of information that is independent of the
             set of original fields.  Information for  one  set  should
             not  automatically be taken from the other.  The interpre-
             tation of multiple "Resent-" fields, of the same type,  is
             undefined.

           In the remainder of this specification, occurrence of  legal
      "Resent-"  fields  are treated identically with the occurrence of

      August 13, 1982              - 19 -                      RFC #822

      Standard for ARPA Internet Text Messages

      fields whose names do not contain this prefix.

      4.3.  TRACE FIELDS

           Trace information is used to provide an audit trail of  mes-
      sage  handling.   In  addition,  it indicates a route back to the
      sender of the message.

           The list of known "via" and  "with"  values  are  registered
      with  the  Network  Information  Center, SRI International, Menlo
      Park, California.

      4.3.1.  RETURN-PATH

         This field  is  added  by  the  final  transport  system  that
         delivers  the message to its recipient.  The field is intended
         to contain definitive information about the address and  route
         back to the message's originator.

         Note:  The "Reply-To" field is added  by  the  originator  and
                serves  to  direct  replies,  whereas the "Return-Path"
                field is used to identify a path back to  the  origina-
                tor.

         While the syntax  indicates  that  a  route  specification  is
         optional,  every attempt should be made to provide that infor-
         mation in this field.

      4.3.2.  RECEIVED

         A copy of this field is added by each transport  service  that
         relays the message.  The information in the field can be quite
         useful for tracing transport problems.

         The names of the sending  and  receiving  hosts  and  time-of-
         receipt may be specified.  The "via" parameter may be used, to
         indicate what physical mechanism the message  was  sent  over,
         such  as  Arpanet or Phonenet, and the "with" parameter may be
         used to indicate the mail-,  or  connection-,  level  protocol
         that  was  used, such as the SMTP mail protocol, or X.25 tran-
         sport protocol.

         Note:  Several "with" parameters may  be  included,  to  fully
                specify the set of protocols that were used.

         Some transport services queue mail; the internal message iden-
         tifier that is assigned to the message may be noted, using the
         "id" parameter.  When the  sending  host  uses  a  destination
         address specification that the receiving host reinterprets, by

      August 13, 1982              - 20 -                      RFC #822

      Standard for ARPA Internet Text Messages

         expansion or transformation, the receiving host  may  wish  to
         record  the original specification, using the "for" parameter.
         For example, when a copy of mail is sent to the  member  of  a
         distribution  list,  this  parameter may be used to record the
         original address that was used to specify the list.

      4.4.  ORIGINATOR FIELDS

           The standard allows only a subset of the combinations possi-
      ble  with the From, Sender, Reply-To, Resent-From, Resent-Sender,
      and Resent-Reply-To fields.  The limitation is intentional.

      4.4.1.  FROM / RESENT-FROM

         This field contains the identity of the person(s)  who  wished
         this  message to be sent.  The message-creation process should
         default this field  to  be  a  single,  authenticated  machine
         address,  indicating  the  AGENT  (person,  system or process)
         entering the message.  If this is not done, the "Sender" field
         MUST  be  present.  If the "From" field IS defaulted this way,
         the "Sender" field is  optional  and  is  redundant  with  the
         "From"  field.   In  all  cases, addresses in the "From" field
         must be machine-usable (addr-specs) and may not contain  named
         lists (groups).

      4.4.2.  SENDER / RESENT-SENDER

         This field contains the authenticated identity  of  the  AGENT
         (person,  system  or  process)  that sends the message.  It is
         intended for use when the sender is not the author of the mes-
         sage,  or  to  indicate  who among a group of authors actually
         sent the message.  If the contents of the "Sender" field would
         be  completely  redundant  with  the  "From"  field,  then the
         "Sender" field need not be present and its use is  discouraged
         (though  still legal).  In particular, the "Sender" field MUST
         be present if it is NOT the same as the "From" Field.

         The Sender mailbox  specification  includes  a  word  sequence
         which  must correspond to a specific agent (i.e., a human user
         or a computer program) rather than a standard  address.   This
         indicates  the  expectation  that  the field will identify the
         single AGENT (person,  system,  or  process)  responsible  for
         sending  the mail and not simply include the name of a mailbox
         from which the mail was sent.  For example in the  case  of  a
         shared login name, the name, by itself, would not be adequate.
         The local-part address unit, which refers to  this  agent,  is
         expected to be a computer system term, and not (for example) a
         generalized person reference which can  be  used  outside  the
         network text message context.

      August 13, 1982              - 21 -                      RFC #822

      Standard for ARPA Internet Text Messages

         Since the critical function served by the  "Sender"  field  is
         identification  of  the agent responsible for sending mail and
         since computer programs cannot be held accountable  for  their
         behavior, it is strongly recommended that when a computer pro-
         gram generates a message, the HUMAN  who  is  responsible  for
         that program be referenced as part of the "Sender" field mail-
         box specification.

      4.4.3.  REPLY-TO / RESENT-REPLY-TO

         This field provides a general  mechanism  for  indicating  any
         mailbox(es)  to which responses are to be sent.  Three typical
         uses for this feature can  be  distinguished.   In  the  first
         case,  the  author(s) may not have regular machine-based mail-
         boxes and therefore wish(es) to indicate an alternate  machine
         address.   In  the  second case, an author may wish additional
         persons to be made aware of, or responsible for,  replies.   A
         somewhat  different  use  may be of some help to "text message
         teleconferencing" groups equipped with automatic  distribution
         services:   include the address of that service in the "Reply-
         To" field of all messages  submitted  to  the  teleconference;
         then  participants  can  "reply"  to conference submissions to
         guarantee the correct distribution of any submission of  their
         own.

         Note:  The "Return-Path" field is added by the mail  transport
                service,  at the time of final deliver.  It is intended
                to identify a path back to the orginator  of  the  mes-
                sage.   The  "Reply-To"  field  is added by the message
                originator and is intended to direct replies.

      4.4.4.  AUTOMATIC USE OF FROM / SENDER / REPLY-TO

         For systems which automatically  generate  address  lists  for
         replies to messages, the following recommendations are made:

             o   The "Sender" field mailbox should be sent  notices  of
                 any  problems in transport or delivery of the original
                 messages.  If there is no  "Sender"  field,  then  the
                 "From" field mailbox should be used.

             o   The  "Sender"  field  mailbox  should  NEVER  be  used
                 automatically, in a recipient's reply message.

             o   If the "Reply-To" field exists, then the reply  should
                 go to the addresses indicated in that field and not to
                 the address(es) indicated in the "From" field.

      August 13, 1982              - 22 -                      RFC #822

      Standard for ARPA Internet Text Messages

             o   If there is a "From" field, but no  "Reply-To"  field,
                 the  reply should be sent to the address(es) indicated
                 in the "From" field.

         Sometimes, a recipient may actually wish to  communicate  with
         the  person  that  initiated  the  message  transfer.  In such
         cases, it is reasonable to use the "Sender" address.

         This recommendation is intended  only  for  automated  use  of
         originator-fields  and is not intended to suggest that replies
         may not also be sent to other recipients of messages.   It  is
         up  to  the  respective  mail-handling programs to decide what
         additional facilities will be provided.

         Examples are provided in Appendix A.

      4.5.  RECEIVER FIELDS

      4.5.1.  TO / RESENT-TO

         This field contains the identity of the primary recipients  of
         the message.

      4.5.2.  CC / RESENT-CC

         This field contains the identity of  the  secondary  (informa-
         tional) recipients of the message.

      4.5.3.  BCC / RESENT-BCC

         This field contains the identity of additional  recipients  of
         the  message.   The contents of this field are not included in
         copies of the message sent to the primary and secondary  reci-
         pients.   Some  systems  may choose to include the text of the
         "Bcc" field only in the author(s)'s  copy,  while  others  may
         also include it in the text sent to all those indicated in the
         "Bcc" list.

      4.6.  REFERENCE FIELDS

      4.6.1.  MESSAGE-ID / RESENT-MESSAGE-ID

              This field contains a unique identifier  (the  local-part
         address  unit)  which  refers to THIS version of THIS message.
         The uniqueness of the message identifier is guaranteed by  the
         host  which  generates  it.  This identifier is intended to be
         machine readable and not necessarily meaningful to humans.   A
         message  identifier pertains to exactly one instantiation of a
         particular message; subsequent revisions to the message should

      August 13, 1982              - 23 -                      RFC #822

      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 <word> parameter  indicates  the
         software  used  to  encrypt the body, and the second, optional
         <word> 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

      August 13, 1982              - 24 -                      RFC #822

      Standard for ARPA Internet Text Messages

                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.

      August 13, 1982              - 25 -                      RFC #822

      Standard for ARPA Internet Text Messages

      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.

      August 13, 1982              - 26 -                      RFC #822

      Standard for ARPA Internet Text Messages

      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.

      August 13, 1982              - 27 -                      RFC #822

      Standard for ARPA Internet Text Messages

         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

      August 13, 1982              - 28 -                      RFC #822

      Standard for ARPA Internet Text Messages

         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

      August 13, 1982              - 29 -                      RFC #822

      Standard for ARPA Internet Text Messages

         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
                <word>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

      August 13, 1982              - 30 -                      RFC #822

      Standard for ARPA Internet Text Messages

         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

      August 13, 1982              - 31 -                      RFC #822

      Standard for ARPA Internet Text Messages

         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 <group> 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 <address>
         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  <group>  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 <route> 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 <Neuman@BBN-TENEXA>

      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" <Shared@Group.Arpanet>

              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 <WhoZiWhatZit@Cordon-Bleu>,
                 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 <Jones@Group.Org>

      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 <Jones@Group>
             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<Shared@Group.Org>
             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 <Jones@Host.Net>
             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 <Group@Host>
             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 <Secy@Registry>
             Sender:   Secy-Name <Secy@Registry>
             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 <group> 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<Group@Host>
      Sender:   Secy@SHOST
      To:       "Al Neuman"@Mad-Host,
                Sam.Irving@Other-Host
      Message-ID:  <some.string@SHOST>

      A.3.3.  About as complex as you're going to get

      Date     :  27 Aug 76 0932 PDT
      From     :  Ken Davis <KDavis@This-Host.This-net>
      Subject  :  Re: The Syntax in the RFC
      Sender   :  KSecy@Other-Host
      Reply-To :  Sam.Irving@Reg.Organization
      To       :  George Jones <Group@Some-Reg.An-Org>,
                  Al.Neuman@MAD.Publisher
      cc       :  Important folk:
                    Tom Softwood <Balsa@Tree.Root>,
                    "Sam Irving"@Other-Host;,
                  Standard Distribution:
                    /main/davis/people/standard@Other-Host,
                    "<Jones>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: <some.string@DBM.Group>, 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*<any CHAR, excluding CTLs, SPACE, and ":">

      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  <domain-literal>  and  <dtext>  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 <route> 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       =  <any ASCII alphabetic character>
                                                  ; (101-132, 65.- 90.)
                                                  ; (141-172, 97.-122.)
      atom        =  1*<any CHAR except specials, SPACE and CTLs>
      authentic   =   "From"       ":"   mailbox  ; Single author
                  / ( "Sender"     ":"   mailbox  ; Actual submittor
                      "From"       ":" 1#mailbox) ; Multiple authors
                                                  ;  or not sender
      CHAR        =  <any ASCII character>        ; (  0-177,  0.-127.)
      comment     =  "(" *(ctext / quoted-pair / comment) ")"
      CR          =  <ASCII CR, carriage return>  ; (     15,      13.)
      CRLF        =  CR LF
      ctext       =  <any CHAR excluding "(",     ; => may be folded
                      ")", "\" & CR, & including
                      linear-white-space>
      CTL         =  <any ASCII control           ; (  0- 37,  0.- 31.)
                      character and DEL>          ; (    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       =  <any ASCII decimal digit>    ; ( 60- 71, 48.- 57.)
      domain      =  sub-domain *("." sub-domain)
      domain-literal =  "[" *(dtext / quoted-pair) "]"
      domain-ref  =  atom                         ; symbolic reference
      dtext       =  <any CHAR excluding "[",     ; => may be folded
                      "]", "\" & CR, & including
                      linear-white-space>
      extension-field =
                    <Any field which is defined in a document
                     published as a formal extension to this
                     specification; none will have names beginning
                     with the string "X-">

      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 =
                    <the ASCII characters making up the field-body, as
                     defined in the following sections, and consisting
                     of combinations of atom, quoted-string, and
                     specials tokens, or else consisting of texts>
      field-name  =  1*<any CHAR, excluding CTLs, SPACE, and ":">
      group       =  phrase ":" [#mailbox] ";"
      hour        =  2DIGIT ":" 2DIGIT [":" 2DIGIT]
                                                  ; 00:00:00 - 23:59:59
      HTAB        =  <ASCII HT, horizontal-tab>   ; (     11,       9.)
      LF          =  <ASCII LF, linefeed>         ; (     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       =  <any CHAR excepting <">,     ; => 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       =  <ASCII SP, space>            ; (     40,      32.)
      specials    =  "(" / ")" / "<" / ">" / "@"  ; Must be in quoted-
                  /  "," / ";" / ":" / "\" / <">  ;  string, to use
                  /  "." / "[" / "]"              ;  within a word.
      sub-domain  =  domain-ref / domain-literal
      text        =  <any CHAR, including bare    ; => 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 =
                    <Any field which has not been defined
                     in this specification or published as an
                     extension to this specification; names for
                     such fields must be unique and may be
                     pre-empted by published extensions>
      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;
      <">         =  <ASCII quote mark>           ; (     42,      34.)

      August 13, 1982              - 47 -                      RFC #822


     ----------------------------------------------------------------------

               [ Index | Search | What's New | Comments | Help ]

    Comments/Questions about this archive ? Send mail to rfc-admin@faqs.org
