# RFC 0822

         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

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         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.

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         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.

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         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.

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         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.

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         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.

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         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

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         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

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            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

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            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.

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         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>

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         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) "]"

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         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

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         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

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            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

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         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

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                            ";"    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

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         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

- Markus Freikamp
- Michael.Bank@FH-Koeln.DE