RFC #  822

Obsoletes:  RFC #733  (NIC #41952)

                   STANDARD FOR THE FORMAT OF

                   ARPA INTERNET TEXT MESSAGES

                         August 13, 1982

                           Revised by

                        David H. Crocker

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

Standard for ARPA Internet Text Messages

                        TABLE OF CONTENTS

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

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

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

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

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

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

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

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

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

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

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

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

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

                        APPENDIX

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

August 13, 1982               - i -                      RFC #822

Standard for ARPA Internet Text Messages

                             PREFACE

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

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

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

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

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

August 13, 1982              - ii -                      RFC #822

Standard for ARPA Internet Text Messages

1.  INTRODUCTION

1.1.  SCOPE

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

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

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

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

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

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

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

August 13, 1982               - 1 -                      RFC #822

Standard for ARPA Internet Text Messages

1.2.  COMMUNICATION FRAMEWORK

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

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

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

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

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

August 13, 1982               - 2 -                      RFC #822

Standard for ARPA Internet Text Messages

2.  NOTATIONAL CONVENTIONS

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

2.1.  RULE NAMING

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

2.2.  RULE1 / RULE2:  ALTERNATIVES

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

2.3.  (RULE1 RULE2):  LOCAL ALTERNATIVES

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

2.4.  *RULE:  REPETITION

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

                         <l>*<m>element

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

2.5.  [RULE]:  OPTIONAL

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

2.6.  NRULE:  SPECIFIC REPETITION

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

August 13, 1982               - 3 -                      RFC #822

Standard for ARPA Internet Text Messages

2.7.  #RULE:  LISTS

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

                         <l>#<m>element

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

2.8.  ; COMMENTS

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

August 13, 1982               - 4 -                      RFC #822

Standard for ARPA Internet Text Messages

3.  LEXICAL ANALYSIS OF MESSAGES

3.1.  GENERAL DESCRIPTION

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

3.1.1.  LONG HEADER FIELDS

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

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

   can be represented as:

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

   and

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

   and

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

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

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

August 13, 1982               - 5 -                      RFC #822

Standard for ARPA Internet Text Messages

          between addresses, after the separating comma.

3.1.2.  STRUCTURE OF HEADER FIELDS

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

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

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

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

3.1.3.  UNSTRUCTURED FIELD BODIES

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

3.1.4.  STRUCTURED FIELD BODIES

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

August 13, 1982               - 6 -                      RFC #822

Standard for ARPA Internet Text Messages

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

   These symbols are:

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

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

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

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

August 13, 1982               - 7 -                      RFC #822

Standard for ARPA Internet Text Messages

   is analyzed into the following lexical symbols and types:

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

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

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

   and

                       Muhammed.Ali@Vegas.WBA

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

August 13, 1982               - 8 -                      RFC #822

Standard for ARPA Internet Text Messages

3.2.  HEADER FIELD DEFINITIONS

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

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

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

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

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

August 13, 1982               - 9 -                      RFC #822

Standard for ARPA Internet Text Messages

3.3.  LEXICAL TOKENS

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

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

LWSP-char   =  SPACE / HTAB                 ; semantics = SPACE

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

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

delimiters  =  specials / linear-white-space / comment

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

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

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

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

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

August 13, 1982              - 10 -                      RFC #822

Standard for ARPA Internet Text Messages

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

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

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

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

phrase      =  1*word                       ; Sequence of words

word        =  atom / quoted-string

3.4.  CLARIFICATIONS

3.4.1.  QUOTING

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

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

                        -  quoted-string
                        -  domain-literal
                        -  comment

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

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

                       Full\ Name@Domain

          is not legal and must be specified as:

                       "Full Name"@Domain

August 13, 1982              - 11 -                      RFC #822

Standard for ARPA Internet Text Messages

3.4.2.  WHITE SPACE

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

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

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

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

3.4.3.  COMMENTS

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

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

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

August 13, 1982              - 12 -                      RFC #822

Standard for ARPA Internet Text Messages

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

3.4.4.  DELIMITING AND QUOTING CHARACTERS

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

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

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

3.4.5.  QUOTED-STRINGS

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

August 13, 1982              - 13 -                      RFC #822

Standard for ARPA Internet Text Messages

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

3.4.6.  BRACKETING CHARACTERS

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

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

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

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

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

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

3.4.7.  CASE INDEPENDENCE

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

August 13, 1982              - 14 -                      RFC #822

Standard for ARPA Internet Text Messages

   which requires preservation of case information are:

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

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

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

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

3.4.8.  FOLDING LONG HEADER FIELDS

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

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

3.4.9.  BACKSPACE CHARACTERS

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

August 13, 1982              - 15 -                      RFC #822

Standard for ARPA Internet Text Messages

3.4.10.  NETWORK-SPECIFIC TRANSFORMATIONS

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

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

       o   Transformation Reversal

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

       o   Transformation

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

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

August 13, 1982              - 16 -                      RFC #822

Standard for ARPA Internet Text Messages

4.  MESSAGE SPECIFICATION

4.1.  SYNTAX

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

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

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

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

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

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

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

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

received    =  "Received"    ":"            ; one per relay
                  ["from" domain]           ; sending host
                  ["by"   domain]           ; receiving host
                  ["via"  atom]             ; physical path
                 *("with" atom)             ; link/mail protocol
                  ["id"   msg-id]           ; receiver msg id
                  ["for"  addr-spec]        ; initial form

August 13, 1982              - 17 -                      RFC #822

Standard for ARPA Internet Text Messages

                   ";"    date-time         ; time received

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

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

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

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

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

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

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

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

optional-field =
            /  "Message-ID"        ":"   msg-id
            /  "Resent-Message-ID" ":"   msg-id
            /  "In-Reply-To"       ":"  *(phrase / msg-id)
            /  "References"        ":"  *(phrase / msg-id)
            /  "Keywords"          ":"  #phrase
            /  "Subject"           ":"  *text
            /  "Comments"          ":"  *text
            /  "Encrypted"         ":" 1#2word
            /  extension-field              ; To be defined
            /  user-defined-field           ; May be pre-empted

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

August 13, 1982              - 18 -                      RFC #822

Standard for ARPA Internet Text Messages

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

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

4.2.  FORWARDING

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

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

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

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

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

August 13, 1982              - 19 -                      RFC #822

Standard for ARPA Internet Text Messages

fields whose names do not contain this prefix.

4.3.  TRACE FIELDS

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

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

4.3.1.  RETURN-PATH

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

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

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

4.3.2.  RECEIVED

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

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

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

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

August 13, 1982              - 20 -                      RFC #822

Standard for ARPA Internet Text Messages

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

4.4.  ORIGINATOR FIELDS

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

4.4.1.  FROM / RESENT-FROM

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

4.4.2.  SENDER / RESENT-SENDER

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

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

August 13, 1982              - 21 -                      RFC #822

Standard for ARPA Internet Text Messages

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

4.4.3.  REPLY-TO / RESENT-REPLY-TO

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

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

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

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

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

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

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

August 13, 1982              - 22 -                      RFC #822

Standard for ARPA Internet Text Messages

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

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

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

   Examples are provided in Appendix A.

4.5.  RECEIVER FIELDS

4.5.1.  TO / RESENT-TO

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

4.5.2.  CC / RESENT-CC

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

4.5.3.  BCC / RESENT-BCC

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

4.6.  REFERENCE FIELDS

4.6.1.  MESSAGE-ID / RESENT-MESSAGE-ID

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

August 13, 1982              - 23 -                      RFC #822

Standard for ARPA Internet Text Messages

   each receive new message identifiers.

4.6.2.  IN-REPLY-TO

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

4.6.3.  REFERENCES

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

4.6.4.  KEYWORDS

        This field contains keywords  or  phrases,  separated  by
   commas.

4.7.  OTHER FIELDS

4.7.1.  SUBJECT

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

4.7.2.  COMMENTS

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

4.7.3.  ENCRYPTED

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

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

August 13, 1982              - 24 -                      RFC #822

Standard for ARPA Internet Text Messages

          sensitive  information,  this  requirement limits total
          message privacy.

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

4.7.4.  EXTENSION-FIELD

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

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

4.7.5.  USER-DEFINED-FIELD

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

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

August 13, 1982              - 25 -                      RFC #822

Standard for ARPA Internet Text Messages

5.  DATE AND TIME SPECIFICATION

5.1.  SYNTAX

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

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

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

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

time        =  hour zone                    ; ANSI and Military

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

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

5.2.  SEMANTICS

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

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

August 13, 1982              - 26 -                      RFC #822

Standard for ARPA Internet Text Messages

6.  ADDRESS SPECIFICATION

6.1.  SYNTAX

address     =  mailbox                      ; one addressee
            /  group                        ; named list

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

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

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

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

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

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

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

sub-domain  =  domain-ref / domain-literal

domain-ref  =  atom                         ; symbolic reference

6.2.  SEMANTICS

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

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

6.2.1.  DOMAINS

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

August 13, 1982              - 27 -                      RFC #822

Standard for ARPA Internet Text Messages

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

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

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

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

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

                    person@registry.organization

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

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

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

                         user@host.network

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

August 13, 1982              - 28 -                      RFC #822

Standard for ARPA Internet Text Messages

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

6.2.2.  ABBREVIATED DOMAIN SPECIFICATION

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

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

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

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

   For example, if a sender's address is:

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

   and one recipient's address is:

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

   and another's is:

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

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

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

August 13, 1982              - 29 -                      RFC #822

Standard for ARPA Internet Text Messages

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

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

6.2.3.  DOMAIN TERMS

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

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

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

                            [10.0.3.19]

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

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

6.2.4.  DOMAIN-DEPENDENT LOCAL STRING

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

August 13, 1982              - 30 -                      RFC #822

Standard for ARPA Internet Text Messages

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

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

   For example, the address:

                      First.Last@Registry.Org

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

6.2.5.  BALANCING LOCAL-PART AND DOMAIN

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

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

                   mailbox.sub1.sub2@this-domain

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

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

                 sub-net.mailbox@sub-domain.domain

August 13, 1982              - 31 -                      RFC #822

Standard for ARPA Internet Text Messages

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

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

6.2.6.  MULTIPLE MAILBOXES

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

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

   While a list must be named, it is not required that  the  con-
   tents  of  the  list be included.  In this case, the <address>
   serves only as an indication of group distribution  and  would
   appear in the form:

                               name:;

   Some mail  services  may  provide  a  group-list  distribution
   facility,  accepting  a single mailbox reference, expanding it
   to the full distribution list, and relaying the  mail  to  the
   list's  members.   This standard provides no additional syntax
   for indicating such a  service.   Using  the  <group>  address
   alternative,  while listing one mailbox in it, can mean either
   that the mailbox reference will be expanded to a list or  that
   there is a group with one member.

6.2.7.  EXPLICIT PATH SPECIFICATION

   At times, a  message  originator  may  wish  to  indicate  the
   transmission  path  that  a  message  should  follow.  This is
   called source routing.  The normal addressing scheme, used  in
   an  addr-spec,  is  carefully separated from such information;
   the <route> portion of a route-addr is provided for such occa-
   sions.  It specifies the sequence of hosts and/or transmission

August 13, 1982              - 32 -                      RFC #822

Standard for ARPA Internet Text Messages

   services that are  to  be  traversed.   Both  domain-refs  and
   domain-literals may be used.

   Note:  The use of source routing is discouraged.   Unless  the
          sender has special need of path restriction, the choice
          of transmission route should be left to the mail  tran-
          sport service.

6.3.  RESERVED ADDRESS

     It often is necessary to send mail to a site, without  know-
ing  any  of its valid addresses.  For example, there may be mail
system dysfunctions, or a user may wish to find  out  a  person's
correct address, at that site.

     This standard specifies a single, reserved  mailbox  address
(local-part)  which  is  to  be valid at each site.  Mail sent to
that address is to be routed to  a  person  responsible  for  the
site's mail system or to a person with responsibility for general
site operation.  The name of the reserved local-part address is:

                           Postmaster

so that "Postmaster@domain" is required to be valid.

Note:  This reserved local-part must be  matched  without  sensi-
       tivity to alphabetic case, so that "POSTMASTER", "postmas-
       ter", and even "poStmASteR" is to be accepted.

August 13, 1982              - 33 -                      RFC #822

Standard for ARPA Internet Text Messages

7.  BIBLIOGRAPHY

ANSI.  "USA Standard Code  for  Information  Interchange,"  X3.4.
   American  National Standards Institute: New York (1968).  Also
   in:  Feinler, E.  and J. Postel, eds., "ARPANET Protocol Hand-
   book", NIC 7104.

ANSI.  "Representations of Universal Time, Local  Time  Differen-
   tials,  and United States Time Zone References for Information
   Interchange," X3.51-1975.  American National Standards  Insti-
   tute:  New York (1975).

Bemer, R.W., "Time and the Computer."  In:  Interface  Age  (Feb.
   1979).

Bennett, C.J.  "JNT Mail Protocol".  Joint Network Team,  Ruther-
   ford and Appleton Laboratory:  Didcot, England.

Bhushan, A.K., Pogran, K.T., Tomlinson,  R.S.,  and  White,  J.E.
   "Standardizing  Network  Mail  Headers,"   ARPANET Request for
   Comments No. 561, Network Information Center  No.  18516;  SRI
   International:  Menlo Park (September 1973).

Birrell, A.D., Levin, R.,  Needham,  R.M.,  and  Schroeder,  M.D.
   "Grapevine:  An Exercise in Distributed Computing," Communica-
   tions of the ACM 25, 4 (April 1982), 260-274.

Crocker,  D.H.,  Vittal,  J.J.,  Pogran,  K.T.,  Henderson,  D.A.
   "Standard  for  the  Format  of  ARPA  Network  Text Message,"
   ARPANET Request for  Comments  No.  733,  Network  Information
   Center  No.  41952.   SRI International:  Menlo Park (November
   1977).

Feinler, E.J. and Postel, J.B.  ARPANET Protocol  Handbook,  Net-
   work  Information  Center  No.  7104   (NTIS AD A003890).  SRI
   International:  Menlo Park (April 1976).

Harary, F.   "Graph  Theory".   Addison-Wesley:   Reading,  Mass.
   (1969).

Levin, R. and Schroeder, M.  "Transport  of  Electronic  Messages
   through  a  Network,"   TeleInformatics  79, pp. 29-33.  North
   Holland (1979).  Also  as  Xerox  Palo  Alto  Research  Center
   Technical Report CSL-79-4.

Myer, T.H. and Henderson, D.A.  "Message Transmission  Protocol,"
   ARPANET  Request  for  Comments,  No. 680, Network Information
   Center No. 32116.  SRI International:  Menlo Park (1975).

August 13, 1982              - 34 -                      RFC #822

Standard for ARPA Internet Text Messages

NBS.  "Specification of Message Format for Computer Based Message
   Systems, Recommended Federal Information Processing Standard."
   National  Bureau   of   Standards:    Gaithersburg,   Maryland
   (October 1981).

NIC.  Internet Protocol Transition Workbook.  Network Information
   Center,   SRI-International,  Menlo  Park,  California  (March
   1982).

Oppen, D.C. and Dalal, Y.K.  "The Clearinghouse:  A Decentralized
   Agent  for  Locating  Named  Objects in a Distributed Environ-
   ment," OPD-T8103.  Xerox Office Products Division:  Palo Alto,
   CA. (October 1981).

Postel, J.B.  "Assigned Numbers,"  ARPANET Request for  Comments,
   No. 820.  SRI International:  Menlo Park (August 1982).

Postel, J.B.  "Simple Mail Transfer  Protocol,"  ARPANET  Request
   for Comments, No. 821.  SRI International:  Menlo Park (August
   1982).

Shoch, J.F.  "Internetwork naming, addressing  and  routing,"  in
   Proc. 17th IEEE Computer Society International Conference, pp.
   72-79, Sept. 1978, IEEE Cat. No. 78 CH 1388-8C.

Su, Z. and Postel, J.  "The Domain Naming Convention for Internet
   User  Applications,"  ARPANET  Request  for Comments, No. 819.
   SRI International:  Menlo Park (August 1982).

August 13, 1982              - 35 -                      RFC #822

Standard for ARPA Internet Text Messages

                            APPENDIX

A.  EXAMPLES

A.1.  ADDRESSES

A.1.1.  Alfred Neuman <Neuman@BBN-TENEXA>

A.1.2.  Neuman@BBN-TENEXA

        These two "Alfred Neuman" examples have identical  seman-
   tics, as far as the operation of the local host's mail sending
   (distribution) program (also sometimes  called  its  "mailer")
   and  the remote host's mail protocol server are concerned.  In
   the first example, the  "Alfred  Neuman"  is  ignored  by  the
   mailer,  as "Neuman@BBN-TENEXA" completely specifies the reci-
   pient.  The second example contains  no  superfluous  informa-
   tion,  and,  again,  "Neuman@BBN-TENEXA" is the intended reci-
   pient.

   Note:  When the message crosses name-domain  boundaries,  then
          these specifications must be changed, so as to indicate
          the remainder of the hierarchy, starting with  the  top
          level.

A.1.3.  "George, Ted" <Shared@Group.Arpanet>

        This form might be used to indicate that a single mailbox
   is  shared  by several users.  The quoted string is ignored by
   the originating host's mailer, because  "Shared@Group.Arpanet"
   completely specifies the destination mailbox.

A.1.4.  Wilt . (the  Stilt) Chamberlain@NBA.US

        The "(the  Stilt)" is a comment, which is NOT included in
   the  destination  mailbox  address  handed  to the originating
   system's mailer.  The local-part of the address is the  string
   "Wilt.Chamberlain", with NO space between the first and second
   words.

A.1.5.  Address Lists

Gourmets:  Pompous Person <WhoZiWhatZit@Cordon-Bleu>,
           Childs@WGBH.Boston, Galloping Gourmet@
           ANT.Down-Under (Australian National Television),
           Cheapie@Discount-Liquors;,
  Cruisers:  Port@Portugal, Jones@SEA;,
    Another@Somewhere.SomeOrg

August 13, 1982              - 36 -                      RFC #822

Standard for ARPA Internet Text Messages

   This group list example points out the use of comments and the
   mixing of addresses and groups.

A.2.  ORIGINATOR ITEMS

A.2.1.  Author-sent

        George Jones logs into his host  as  "Jones".   He  sends
   mail himself.

       From:  Jones@Group.Org

   or

       From:  George Jones <Jones@Group.Org>

A.2.2.  Secretary-sent

        George Jones logs in as Jones on his  host.   His  secre-
   tary,  who logs in as Secy sends mail for him.  Replies to the
   mail should go to George.

       From:    George Jones <Jones@Group>
       Sender:  Secy@Other-Group

A.2.3.  Secretary-sent, for user of shared directory

        George Jones' secretary sends mail  for  George.  Replies
   should go to George.

       From:     George Jones<Shared@Group.Org>
       Sender:   Secy@Other-Group

   Note that there need not be a space between  "Jones"  and  the
   "<",  but  adding a space enhances readability (as is the case
   in other examples.

A.2.4.  Committee activity, with one author

        George is a member of a committee.  He wishes to have any
   replies to his message go to all committee members.

       From:     George Jones <Jones@Host.Net>
       Sender:   Jones@Host
       Reply-To: The Committee: Jones@Host.Net,
                                Smith@Other.Org,
                                Doe@Somewhere-Else;

   Note  that  if  George  had  not  included  himself   in   the

August 13, 1982              - 37 -                      RFC #822

Standard for ARPA Internet Text Messages

   enumeration  of  The  Committee,  he  would not have gotten an
   implicit reply; the presence of the  "Reply-to"  field  SUPER-
   SEDES the sending of a reply to the person named in the "From"
   field.

A.2.5.  Secretary acting as full agent of author

        George Jones asks his secretary  (Secy@Host)  to  send  a
   message for him in his capacity as Group.  He wants his secre-
   tary to handle all replies.

       From:     George Jones <Group@Host>
       Sender:   Secy@Host
       Reply-To: Secy@Host

A.2.6.  Agent for user without online mailbox

        A friend  of  George's,  Sarah,  is  visiting.   George's
   secretary  sends  some  mail to a friend of Sarah in computer-
   land.  Replies should go to George, whose mailbox is Jones  at
   Registry.

       From:     Sarah Friendly <Secy@Registry>
       Sender:   Secy-Name <Secy@Registry>
       Reply-To: Jones@Registry.

A.2.7.  Agent for member of a committee

        George's secretary sends out a message which was authored
   jointly by all the members of a committee.  Note that the name
   of the committee cannot be specified, since <group> names  are
   not permitted in the From field.

       From:   Jones@Host,
               Smith@Other-Host,
               Doe@Somewhere-Else
       Sender: Secy@SHost

August 13, 1982              - 38 -                      RFC #822

Standard for ARPA Internet Text Messages

A.3.  COMPLETE HEADERS

A.3.1.  Minimum required

Date:     26 Aug 76 1429 EDT        Date:     26 Aug 76 1429 EDT
From:     Jones@Registry.Org   or   From:     Jones@Registry.Org
Bcc:                                To:       Smith@Registry.Org

   Note that the "Bcc" field may be empty, while the  "To"  field
   is required to have at least one address.

A.3.2.  Using some of the additional fields

Date:     26 Aug 76 1430 EDT
From:     George Jones<Group@Host>
Sender:   Secy@SHOST
To:       "Al Neuman"@Mad-Host,
          Sam.Irving@Other-Host
Message-ID:  <some.string@SHOST>

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

Date     :  27 Aug 76 0932 PDT
From     :  Ken Davis <KDavis@This-Host.This-net>
Subject  :  Re: The Syntax in the RFC
Sender   :  KSecy@Other-Host
Reply-To :  Sam.Irving@Reg.Organization
To       :  George Jones <Group@Some-Reg.An-Org>,
            Al.Neuman@MAD.Publisher
cc       :  Important folk:
              Tom Softwood <Balsa@Tree.Root>,
              "Sam Irving"@Other-Host;,
            Standard Distribution:
              /main/davis/people/standard@Other-Host,
              "<Jones>standard.dist.3"@Tops-20-Host>;
Comment  :  Sam is away on business. He asked me to handle
            his mail for him.  He'll be able to provide  a
            more  accurate  explanation  when  he  returns
            next week.
In-Reply-To: <some.string@DBM.Group>, George's message
X-Special-action:  This is a sample of user-defined field-
            names.  There could also be a field-name
            "Special-action", but its name might later be
            preempted
Message-ID: <4231.629.XYzi-What@Other-Host>

August 13, 1982              - 39 -                      RFC #822

Standard for ARPA Internet Text Messages

B.  SIMPLE FIELD PARSING

     Some mail-reading software systems may wish to perform  only
minimal  processing,  ignoring  the internal syntax of structured
field-bodies and treating them the  same  as  unstructured-field-
bodies.  Such software will need only to distinguish:

    o   Header fields from the message body,

    o   Beginnings of fields from lines which continue fields,

    o   Field-names from field-contents.

     The abbreviated set of syntactic rules  which  follows  will
suffice  for  this  purpose.  It describes a limited view of mes-
sages and is a subset of the syntactic rules provided in the main
part of this specification.  One small exception is that the con-
tents of field-bodies consist only of text:

B.1.  SYNTAX

message         =   *field *(CRLF *text)

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

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

field-body      =   *text [CRLF LWSP-char field-body]

B.2.  SEMANTICS

     Headers occur before the message body and are terminated  by
a null line (i.e., two contiguous CRLFs).

     A line which continues a header field begins with a SPACE or
HTAB  character,  while  a  line  beginning a field starts with a
printable character which is not a colon.

     A field-name consists of one or  more  printable  characters
(excluding  colon,  space, and control-characters).  A field-name
MUST be contained on one line.  Upper and lower case are not dis-
tinguished when comparing field-names.

August 13, 1982              - 40 -                      RFC #822

Standard for ARPA Internet Text Messages

C.  DIFFERENCES FROM RFC #733

     The following summarizes the differences between this  stan-
dard  and the one specified in Arpanet Request for Comments #733,
"Standard for the Format of ARPA  Network  Text  Messages".   The
differences  are  listed  in the order of their occurrence in the
current specification.

C.1.  FIELD DEFINITIONS

C.1.1.  FIELD NAMES

   These now must be a sequence of  printable  characters.   They
   may not contain any LWSP-chars.

C.2.  LEXICAL TOKENS

C.2.1.  SPECIALS

   The characters period ("."), left-square  bracket  ("["),  and
   right-square  bracket ("]") have been added.  For presentation
   purposes, and when passing a specification to  a  system  that
   does  not conform to this standard, periods are to be contigu-
   ous with their surrounding lexical tokens.   No  linear-white-
   space  is  permitted  between them.  The presence of one LWSP-
   char between other tokens is still directed.

C.2.2.  ATOM

   Atoms may not contain SPACE.

C.2.3.  SPECIAL TEXT

   ctext and qtext have had backslash ("\") added to the list  of
   prohibited characters.

C.2.4.  DOMAINS

   The lexical tokens  <domain-literal>  and  <dtext>  have  been
   added.

C.3.  MESSAGE SPECIFICATION

C.3.1.  TRACE

   The "Return-path:" and "Received:" fields have been specified.

August 13, 1982              - 41 -                      RFC #822

Standard for ARPA Internet Text Messages

C.3.2.  FROM

   The "From" field must contain machine-usable addresses  (addr-
   spec).   Multiple  addresses may be specified, but named-lists
   (groups) may not.

C.3.3.  RESENT

   The meta-construct of prefacing field names  with  the  string
   "Resent-"  has been added, to indicate that a message has been
   forwarded by an intermediate recipient.

C.3.4.  DESTINATION

   A message must contain at least one destination address field.
   "To" and "CC" are required to contain at least one address.

C.3.5.  IN-REPLY-TO

   The field-body is no longer a comma-separated list, although a
   sequence is still permitted.

C.3.6.  REFERENCE

   The field-body is no longer a comma-separated list, although a
   sequence is still permitted.

C.3.7.  ENCRYPTED

   A field has been specified that permits  senders  to  indicate
   that the body of a message has been encrypted.

C.3.8.  EXTENSION-FIELD

   Extension fields are prohibited from beginning with the  char-
   acters "X-".

C.4.  DATE AND TIME SPECIFICATION

C.4.1.  SIMPLIFICATION

   Fewer optional forms are permitted  and  the  list  of  three-
   letter time zones has been shortened.

C.5.  ADDRESS SPECIFICATION

August 13, 1982              - 42 -                      RFC #822

Standard for ARPA Internet Text Messages

C.5.1.  ADDRESS

   The use of quoted-string, and the ":"-atom-":" construct, have
   been  removed.   An  address  now  is  either a single mailbox
   reference or is a named list of addresses.  The  latter  indi-
   cates a group distribution.

C.5.2.  GROUPS

   Group lists are now required to to have a name.   Group  lists
   may not be nested.

C.5.3.  MAILBOX

   A mailbox specification  may  indicate  a  person's  name,  as
   before.   Such  a  named  list  no longer may specify multiple
   mailboxes and may not be nested.

C.5.4.  ROUTE ADDRESSING

   Addresses now are taken to be absolute, global specifications,
   independent  of transmission paths.  The <route> construct has
   been provided, to permit explicit specification  of  transmis-
   sion  path.   RFC  #733's  use  of multiple at-signs ("@") was
   intended as a general syntax  for  indicating  routing  and/or
   hierarchical addressing.  The current standard separates these
   specifications and only one at-sign is permitted.

C.5.5.  AT-SIGN

   The string " at " no longer is used as an  address  delimiter.
   Only at-sign ("@") serves the function.

C.5.6.  DOMAINS

   Hierarchical, logical name-domains have been added.

C.6.  RESERVED ADDRESS

The local-part "Postmaster" has been reserved, so that users  can
be guaranteed at least one valid address at a site.

August 13, 1982              - 43 -                      RFC #822

Standard for ARPA Internet Text Messages

D.  ALPHABETICAL LISTING OF SYNTAX RULES

address     =  mailbox                      ; one addressee
            /  group                        ; named list
addr-spec   =  local-part "@" domain        ; global address
ALPHA       =  <any ASCII alphabetic character>
                                            ; (101-132, 65.- 90.)
                                            ; (141-172, 97.-122.)
atom        =  1*<any CHAR except specials, SPACE and CTLs>
authentic   =   "From"       ":"   mailbox  ; Single author
            / ( "Sender"     ":"   mailbox  ; Actual submittor
                "From"       ":" 1#mailbox) ; Multiple authors
                                            ;  or not sender
CHAR        =  <any ASCII character>        ; (  0-177,  0.-127.)
comment     =  "(" *(ctext / quoted-pair / comment) ")"
CR          =  <ASCII CR, carriage return>  ; (     15,      13.)
CRLF        =  CR LF
ctext       =  <any CHAR excluding "(",     ; => may be folded
                ")", "\" & CR, & including
                linear-white-space>
CTL         =  <any ASCII control           ; (  0- 37,  0.- 31.)
                character and DEL>          ; (    177,     127.)
date        =  1*2DIGIT month 2DIGIT        ; day month year
                                            ;  e.g. 20 Jun 82
dates       =   orig-date                   ; Original
              [ resent-date ]               ; Forwarded
date-time   =  [ day "," ] date time        ; dd mm yy
                                            ;  hh:mm:ss zzz
day         =  "Mon"  / "Tue" /  "Wed"  / "Thu"
            /  "Fri"  / "Sat" /  "Sun"
delimiters  =  specials / linear-white-space / comment
destination =  "To"          ":" 1#address  ; Primary
            /  "Resent-To"   ":" 1#address
            /  "cc"          ":" 1#address  ; Secondary
            /  "Resent-cc"   ":" 1#address
            /  "bcc"         ":"  #address  ; Blind carbon
            /  "Resent-bcc"  ":"  #address
DIGIT       =  <any ASCII decimal digit>    ; ( 60- 71, 48.- 57.)
domain      =  sub-domain *("." sub-domain)
domain-literal =  "[" *(dtext / quoted-pair) "]"
domain-ref  =  atom                         ; symbolic reference
dtext       =  <any CHAR excluding "[",     ; => may be folded
                "]", "\" & CR, & including
                linear-white-space>
extension-field =
              <Any field which is defined in a document
               published as a formal extension to this
               specification; none will have names beginning
               with the string "X-">

August 13, 1982              - 44 -                      RFC #822

Standard for ARPA Internet Text Messages

field       =  field-name ":" [ field-body ] CRLF
fields      =    dates                      ; Creation time,
                 source                     ;  author id & one
               1*destination                ;  address required
                *optional-field             ;  others optional
field-body  =  field-body-contents
               [CRLF LWSP-char field-body]
field-body-contents =
              <the ASCII characters making up the field-body, as
               defined in the following sections, and consisting
               of combinations of atom, quoted-string, and
               specials tokens, or else consisting of texts>
field-name  =  1*<any CHAR, excluding CTLs, SPACE, and ":">
group       =  phrase ":" [#mailbox] ";"
hour        =  2DIGIT ":" 2DIGIT [":" 2DIGIT]
                                            ; 00:00:00 - 23:59:59
HTAB        =  <ASCII HT, horizontal-tab>   ; (     11,       9.)
LF          =  <ASCII LF, linefeed>         ; (     12,      10.)
linear-white-space =  1*([CRLF] LWSP-char)  ; semantics = SPACE
                                            ; CRLF => folding
local-part  =  word *("." word)             ; uninterpreted
                                            ; case-preserved
LWSP-char   =  SPACE / HTAB                 ; semantics = SPACE
mailbox     =  addr-spec                    ; simple address
            /  phrase route-addr            ; name & addr-spec
message     =  fields *( CRLF *text )       ; Everything after
                                            ;  first null line
                                            ;  is message body
month       =  "Jan"  /  "Feb" /  "Mar"  /  "Apr"
            /  "May"  /  "Jun" /  "Jul"  /  "Aug"
            /  "Sep"  /  "Oct" /  "Nov"  /  "Dec"
msg-id      =  "<" addr-spec ">"            ; Unique message id
optional-field =
            /  "Message-ID"        ":"   msg-id
            /  "Resent-Message-ID" ":"   msg-id
            /  "In-Reply-To"       ":"  *(phrase / msg-id)
            /  "References"        ":"  *(phrase / msg-id)
            /  "Keywords"          ":"  #phrase
            /  "Subject"           ":"  *text
            /  "Comments"          ":"  *text
            /  "Encrypted"         ":" 1#2word
            /  extension-field              ; To be defined
            /  user-defined-field           ; May be pre-empted
orig-date   =  "Date"        ":"   date-time
originator  =   authentic                   ; authenticated addr
              [ "Reply-To"   ":" 1#address] )
phrase      =  1*word                       ; Sequence of words

August 13, 1982              - 45 -                      RFC #822

Standard for ARPA Internet Text Messages

qtext       =  <any CHAR excepting <">,     ; => may be folded
                "\" & CR, and including
                linear-white-space>
quoted-pair =  "\" CHAR                     ; may quote any char
quoted-string = <"> *(qtext/quoted-pair) <">; Regular qtext or
                                            ;   quoted chars.
received    =  "Received"    ":"            ; one per relay
                  ["from" domain]           ; sending host
                  ["by"   domain]           ; receiving host
                  ["via"  atom]             ; physical path
                 *("with" atom)             ; link/mail protocol
                  ["id"   msg-id]           ; receiver msg id
                  ["for"  addr-spec]        ; initial form
                   ";"    date-time         ; time received

resent      =   resent-authentic
              [ "Resent-Reply-To"  ":" 1#address] )
resent-authentic =
            =   "Resent-From"      ":"   mailbox
            / ( "Resent-Sender"    ":"   mailbox
                "Resent-From"      ":" 1#mailbox  )
resent-date =  "Resent-Date" ":"   date-time
return      =  "Return-path" ":" route-addr ; return address
route       =  1#("@" domain) ":"           ; path-relative
route-addr  =  "<" [route] addr-spec ">"
source      = [  trace ]                    ; net traversals
                 originator                 ; original mail
              [  resent ]                   ; forwarded
SPACE       =  <ASCII SP, space>            ; (     40,      32.)
specials    =  "(" / ")" / "<" / ">" / "@"  ; Must be in quoted-
            /  "," / ";" / ":" / "\" / <">  ;  string, to use
            /  "." / "[" / "]"              ;  within a word.
sub-domain  =  domain-ref / domain-literal
text        =  <any CHAR, including bare    ; => atoms, specials,
                CR & bare LF, but NOT       ;  comments and
                including CRLF>             ;  quoted-strings are
                                            ;  NOT recognized.
time        =  hour zone                    ; ANSI and Military
trace       =    return                     ; path to sender
               1*received                   ; receipt tags
user-defined-field =
              <Any field which has not been defined
               in this specification or published as an
               extension to this specification; names for
               such fields must be unique and may be
               pre-empted by published extensions>
word        =  atom / quoted-string

August 13, 1982              - 46 -                      RFC #822

Standard for ARPA Internet Text Messages

zone        =  "UT"  / "GMT"                ; Universal Time
                                            ; North American : UT
            /  "EST" / "EDT"                ;  Eastern:  - 5/ - 4
            /  "CST" / "CDT"                ;  Central:  - 6/ - 5
            /  "MST" / "MDT"                ;  Mountain: - 7/ - 6
            /  "PST" / "PDT"                ;  Pacific:  - 8/ - 7
            /  1ALPHA                       ; Military: Z = UT;
<">         =  <ASCII quote mark>           ; (     42,      34.)

August 13, 1982              - 47 -                      RFC #822

Home

Features

NeoMutt Guide

Downloads

Contrib

Manual Pages

Development

Code Docs

RFCs

Management

Search by Algolia