

 









     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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                                  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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     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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     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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               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





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        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

















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        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.











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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

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























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     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





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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













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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

















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     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





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        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





 

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        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.









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            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





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        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





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               sensitive  information,  this  requirement limits total

               message privacy.



             Names of encryption software are registered with the Net-

        work  Information Center, SRI International, Menlo Park, Cali-

        fornia.



     4.7.4.  EXTENSION-FIELD



             A limited number of common fields have  been  defined  in

        this  document.   As  network mail requirements dictate, addi-

        tional fields may be standardized.   To  provide  user-defined

        fields  with  a  measure  of  safety,  in name selection, such

        extension-fields will never have names  that  begin  with  the

        string "X-".



             Names of Extension-fields are registered with the Network

        Information Center, SRI International, Menlo Park, California.



     4.7.5.  USER-DEFINED-FIELD



             Individual users of network mail are free to  define  and

        use  additional  header  fields.   Such fields must have names

        which are not already used in the current specification or  in

        any definitions of extension-fields, and the overall syntax of

        these user-defined-fields must conform to this specification's

        rules   for   delimiting  and  folding  fields.   Due  to  the

        extension-field  publishing  process,  the  name  of  a  user-

        defined-field may be pre-empted



        Note:  The prefatory string "X-" will never  be  used  in  the

               names  of Extension-fields.  This provides user-defined

               fields with a protected set of names.





































     August 13, 1982              - 25 -                      RFC #822





 

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     5.  DATE AND TIME SPECIFICATION



     5.1.  SYNTAX



     date-time   =  [ day "," ] date time        ; dd mm yy

                                                 ;  hh:mm:ss zzz



     day         =  "Mon"  / "Tue" /  "Wed"  / "Thu"

                 /  "Fri"  / "Sat" /  "Sun"



     date        =  1*2DIGIT month 2DIGIT        ; day month year

                                                 ;  e.g. 20 Jun 82



     month       =  "Jan"  /  "Feb" /  "Mar"  /  "Apr"

                 /  "May"  /  "Jun" /  "Jul"  /  "Aug"

                 /  "Sep"  /  "Oct" /  "Nov"  /  "Dec"



     time        =  hour zone                    ; ANSI and Military



     hour        =  2DIGIT ":" 2DIGIT [":" 2DIGIT]

                                                 ; 00:00:00 - 23:59:59



     zone        =  "UT"  / "GMT"                ; Universal Time

                                                 ; North American : UT

                 /  "EST" / "EDT"                ;  Eastern:  - 5/ - 4

                 /  "CST" / "CDT"                ;  Central:  - 6/ - 5

                 /  "MST" / "MDT"                ;  Mountain: - 7/ - 6

                 /  "PST" / "PDT"                ;  Pacific:  - 8/ - 7

                 /  1ALPHA                       ; Military: Z = UT;

                                                 ;  A:-1; (J not used)

                                                 ;  M:-12; N:+1; Y:+12

                 / ( ("+" / "-") 4DIGIT )        ; Local differential

                                                 ;  hours+min. (HHMM)



     5.2.  SEMANTICS



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

     specification.



          Time zone may be indicated in several ways.  "UT" is Univer-

     sal  Time  (formerly called "Greenwich Mean Time"); "GMT" is per-

     mitted as a reference to Universal Time.  The  military  standard

     uses  a  single  character for each zone.  "Z" is Universal Time.

     "A" indicates one hour earlier, and "M" indicates 12  hours  ear-

     lier;  "N"  is  one  hour  later, and "Y" is 12 hours later.  The

     letter "J" is not used.  The other remaining two forms are  taken

     from ANSI standard X3.51-1975.  One allows explicit indication of

     the amount of offset from UT; the other uses  common  3-character

     strings for indicating time zones in North America.





     August 13, 1982              - 26 -                      RFC #822





 

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     6.  ADDRESS SPECIFICATION



     6.1.  SYNTAX



     address     =  mailbox                      ; one addressee

                 /  group                        ; named list



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



     mailbox     =  addr-spec                    ; simple address

                 /  phrase route-addr            ; name & addr-spec



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



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



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



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

                                                 ; case-preserved



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



     sub-domain  =  domain-ref / domain-literal



     domain-ref  =  atom                         ; symbolic reference



     6.2.  SEMANTICS



          A mailbox receives mail.  It is a  conceptual  entity  which

     does  not necessarily pertain to file storage.  For example, some

     sites may choose to print mail on their line printer and  deliver

     the output to the addressee's desk.



          A mailbox specification comprises a person, system  or  pro-

     cess name reference, a domain-dependent string, and a name-domain

     reference.  The name reference is optional and is usually used to

     indicate  the  human name of a recipient.  The name-domain refer-

     ence specifies a sequence of sub-domains.   The  domain-dependent

     string is uninterpreted, except by the final sub-domain; the rest

     of the mail service merely transmits it as a literal string.



     6.2.1.  DOMAINS



        A name-domain is a set of registered (mail)  names.   A  name-

        domain  specification  resolves  to  a subordinate name-domain

        specification  or  to  a  terminal  domain-dependent   string.

        Hence,  domain  specification  is  extensible,  permitting any

        number of registration levels.





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        Name-domains model a global, logical, hierarchical  addressing

        scheme.   The  model is logical, in that an address specifica-

        tion is related to name registration and  is  not  necessarily

        tied  to  transmission  path.   The  model's  hierarchy  is  a

        directed graph, called an in-tree, such that there is a single

        path  from  the root of the tree to any node in the hierarchy.

        If more than one path actually exists, they are considered  to

        be different addresses.



        The root node is common to all addresses; consequently, it  is

        not  referenced.   Its  children  constitute "top-level" name-

        domains.  Usually, a service has access to its own full domain

        specification and to the names of all top-level name-domains.



        The "top" of the domain addressing hierarchy -- a child of the

        root  --  is  indicated  by  the right-most field, in a domain

        specification.  Its child is specified to the left, its  child

        to the left, and so on.



        Some groups provide formal registration services;  these  con-

        stitute   name-domains   that  are  independent  logically  of

        specific machines.  In addition, networks and machines  impli-

        citly  compose name-domains, since their membership usually is

        registered in name tables.



        In the case of formal registration, an organization implements

        a  (distributed)  data base which provides an address-to-route

        mapping service for addresses of the form:



                         person@registry.organization



        Note that "organization" is a logical  entity,  separate  from

        any particular communication network.



        A mechanism for accessing "organization" is universally avail-

        able.   That mechanism, in turn, seeks an instantiation of the

        registry; its location is not indicated in the address specif-

        ication.   It  is assumed that the system which operates under

        the name "organization" knows how to find a subordinate regis-

        try.  The registry will then use the "person" string to deter-

        mine where to send the mail specification.



        The latter,  network-oriented  case  permits  simple,  direct,

        attachment-related address specification, such as:



                              user@host.network



        Once the network is accessed, it is expected  that  a  message

        will  go  directly  to the host and that the host will resolve





     August 13, 1982              - 28 -                      RFC #822





 

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



     6.2.2.  ABBREVIATED DOMAIN SPECIFICATION



        Since any number of  levels  is  possible  within  the  domain

        hierarchy,  specification  of  a  fully  qualified address can

        become inconvenient.  This standard permits abbreviated domain

        specification, in a special case:



            For the address of  the  sender,  call  the  left-most

            sub-domain  Level  N.   In a header address, if all of

            the sub-domains above (i.e., to the right of) Level  N

            are  the same as those of the sender, then they do not

            have to appear in the specification.   Otherwise,  the

            address must be fully qualified.



            This feature is subject  to  approval  by  local  sub-

            domains.   Individual  sub-domains  may  require their

            member systems, which originate mail, to provide  full

            domain  specification only.  When permitted, abbrevia-

            tions may be present  only  while  the  message  stays

            within the sub-domain of the sender.



            Use of this mechanism requires the sender's sub-domain

            to reserve the names of all top-level domains, so that

            full specifications can be distinguished from abbrevi-

            ated specifications.



        For example, if a sender's address is:



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



        and one recipient's address is:



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



        and another's is:



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



        then ".registry-1.organization-X" need not be specified in the

        the  message,  but  "registry-C.registry-2"  DOES  have  to be

        specified.  That is, the first two addresses may  be  abbrevi-

        ated, but the third address must be fully specified.



        When a message crosses a domain boundary, all  addresses  must

        be  specified  in  the  full format, ending with the top-level

        name-domain in the right-most field.  It is the responsibility

        of  mail  forwarding services to ensure that addresses conform





     August 13, 1982              - 29 -                      RFC #822





 

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        with this requirement.  In the case of abbreviated  addresses,

        the  relaying  service must make the necessary expansions.  It

        should be noted that it often is difficult for such a  service

        to locate all occurrences of address abbreviations.  For exam-

        ple, it will not be possible to find such abbreviations within

        the  body  of  the  message.   The "Return-Path" field can aid

        recipients in recovering from these errors.



        Note:  When passing any portion of an addr-spec onto a process

               which  does  not interpret data according to this stan-

               dard (e.g., mail protocol servers).  There must  be  NO

               LWSP-chars  preceding  or  following the at-sign or any

               delimiting period ("."), such as  shown  in  the  above

               examples,   and   only  ONE  SPACE  between  contiguous

               <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





 

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        whatever the receiving mail protocol server allows.  For exam-

        ple,  some systems do not understand mailbox references of the

        form "P. D. Q. Bach", but others do.



        This specification treats periods (".") as lexical separators.

        Hence,  their  presence  in  local-parts which are not quoted-

        strings, is detected.   However,  such  occurrences  carry  NO

        semantics.  That is, if a local-part has periods within it, an

        address parser will divide the local-part into several tokens,

        but  the  sequence  of  tokens will be treated as one uninter-

        preted unit.  The sequence  will  be  re-assembled,  when  the

        address is passed outside of the system such as to a mail pro-

        tocol service.



        For example, the address:



                           First.Last@Registry.Org



        is legal and does not require the local-part to be  surrounded

        with  quotation-marks.   (However,  "First  Last" DOES require

        quoting.)  The local-part of the address, when passed  outside

        of  the  mail  system,  within  the  Registry.Org  domain,  is

        "First.Last", again without quotation marks.



     6.2.5.  BALANCING LOCAL-PART AND DOMAIN



        In some cases, the boundary between local-part and domain  can

        be  flexible.  The local-part may be a simple string, which is

        used for the final determination of the  recipient's  mailbox.

        All  other  levels  of  reference  are, therefore, part of the

        domain.



        For some systems, in the case of abbreviated reference to  the

        local  and  subordinate  sub-domains,  it  may  be possible to

        specify only one reference within the domain  part  and  place

        the  other,  subordinate  name-domain  references  within  the

        local-part.  This would appear as:



                        mailbox.sub1.sub2@this-domain



        Such a specification would be acceptable  to  address  parsers

        which  conform  to  RFC  #733,  but  do not support this newer

        Internet standard.  While contrary to the intent of this stan-

        dard, the form is legal.



        Also, some sub-domains have a specification syntax which  does

        not conform to this standard.  For example:



                      sub-net.mailbox@sub-domain.domain





     August 13, 1982              - 31 -                      RFC #822





 

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        uses a different parsing  sequence  for  local-part  than  for

        domain.



        Note:  As a rule,  the  domain  specification  should  contain

               fields  which  are  encoded  according to the syntax of

               this standard and which contain  generally-standardized

               information.   The local-part specification should con-

               tain only that portion of the  address  which  deviates

               from the form or intention of the domain field.



     6.2.6.  MULTIPLE MAILBOXES



        An individual may have several mailboxes and wish  to  receive

        mail  at  whatever  mailbox  is  convenient  for the sender to

        access.  This standard does not provide a means of  specifying

        "any member of" a list of mailboxes.



        A set of individuals may wish to receive mail as a single unit

        (i.e.,  a  distribution  list).  The <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





 

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        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





 

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     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





 

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     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





 

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                                 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





 

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        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





 

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        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





 

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     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>













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     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.















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     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.











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     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













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     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





 

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     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





 

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     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





 

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     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





 

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     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



