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Standard for the format of ARPA network text messages :: RFC0733

RFC #   733
NIC # 41952

Obsoletes:  RFC #561  (NIC #18516)
            RFC #680  (NIC #32116)
            RFC #724  (NIC #37435)

                   STANDARD FOR THE FORMAT OF

                  ARPA NETWORK TEXT MESSAGES(1)

                        21 November 1977


                        David H. Crocker
                      The Rand Corporation

                         John J. Vittal
                  Bolt Beranek and Newman Inc.

                        Kenneth T. Pogran
              Massachusets Institute of Technology

                   D. Austin Henderson, Jr.(2)
                  Bolt Beranek and Newman Inc.

(1)This work was  supported  by  the  Defense  Advanced  Research
Projects Agency of the Department of Defense, under contract Nos.
N00014-75-C-0661, MDA903-76-C-0212, and DAHC15-73-C0181.

(2)The authors' postal  addresses  are:   D.  Crocker,  The  Rand
Corporation,  Information  Sciences  Dept.,  1700 Main St., Santa
Monica, California 90406; J.  Vittal  &  D.  A.  Henderson,  Bolt
Beranek & Newman, 50 Moulton St., Cambridge, Massachusetts 02138;
and  K.  Pogran,  MIT  Laboratory  for  Computer   Science,   545
Technology  Square, Cambridge, Massachusetts 02139.  The authors'
ARPANET addresses are:  DCrocker at  Rand-Unix,  Vittal  at  BBN-
TenexD, Pogran at MIT-Multics, and Henderson at BBN-TenexD.


     ARPA's  Committee  on  Computer-Aided  Human   Communication
(CAHCOM)  wishes  to promulgate a standard for the format of ARPA
Network text message (mail) headers which  will  reasonably  meet
the  needs  of  the  various  message  service  subsystems on the
Network today.  The  authors  of  this  document  constitute  the
CAHCOM  subcommittee charged with the task of developing this new

     Essentially, we specify a revision to  ARPANET  Request  for
Comments (RFC) 561, "Standardizing Network Mail Headers", and RFC
680, "Message Transmission Protocol".  This revision removes  and
compacts  portions  of  the  previous  syntax  and  adds  several
features to network address  specification.   In  particular,  we
focus  on  people  and  not  mailboxes  as  recipients  and allow
reference to stored address lists.   We  expect  this  syntax  to
provide  sufficient  capabilities  to  meet most users' immediate
needs and, therefore, give developers enough  breathing  room  to
produce  a new mail transmission protocol "properly".  We believe
that there is enough of a consensus in the Network  community  in
favor  of such a standard syntax to make possible its adoption at
this time.  An earlier draft of this specification was  published
as  RFC  #724, "Proposed Official Standard for the Format of ARPA
Network Messages"  and  contained  extensive  discussion  of  the
background and issues in ARPANET mail standards.

     This specification was developed  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,
participated in this discussion and we would like to  acknowledge
their  considerable  efforts.   The  syntax  of  the standard 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  which  compacts  the
specification and allows increased comprehensibility.



PREFACE..................................................... iii

   I.  INTRODUCTION.........................................   1

  II.  FRAMEWORK............................................   2

 III.  SYNTAX...............................................   4
       A. Notational Conventions............................   4
       B. Lexical Analysis of Messages......................   5
       C. General Syntax of Messages........................  13
       D. Syntax of General Addressee Items.................  15
       E. Supporting Constructs.............................  15

  IV.  SEMANTICS............................................  17
       A. Address Fields....................................  17
       B. Reference Specification Fields....................  22
       C. Other Fields and Syntactic Items..................  23
       D. Dates and Times...................................  24

   V.  EXAMPLES.............................................  25
       A. Addresses.........................................  25
       B. Address Lists.....................................  26
       C. Originator Items..................................  26
       D. Complete Headers..................................  28

   B.  SIMPLE PARSING.......................................  35

BIBLIOGRAPHY................................................  37

Standard for the Format of Text Messages                        1
I. Introduction

                        I.  INTRODUCTION

     This standard specifies a syntax for text messages which are
passed between computer users within the framework of "electronic
mail".  The standard supersedes the informal standards  specified
in  ARPANET  Request  for  Comments  numbers  561, "Standardizing
Network Mail Headers", and 680, "Message Transmission  Protocol".
In  this  document,  a  general framework is first described; the
formal syntax is then specified, followed by a discussion of  the
semantics.  Finally, a number of examples are given.

     This specification is intended strictly as a  definition  of
what  is  to  be  passed between hosts on the ARPANET.  It is NOT
intended to dictate either features which systems on the  Network
are  expected  to support, or user interfaces to message creating
or reading programs.

     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.  These simplifications facilitate the formal
specification and indicate what the OFFICIAL  semantics  are  for
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.

Standard for the Format of Text Messages                        2
II. Framework

                         II.  FRAMEWORK

     Since there are many message systems which exist outside the
ARPANET environment, as well as those within it, it may be useful
to consider the general framework, and resulting capabilities and
limitations, provided by this standard.

     Messages are expected to  consist  of  lines  of  text.   No
special provisions are made, at this time, for encoding drawings,
facsimile, speech, or structured text.

     No significant consideration has been given to questions  of
data   compression   or   transmission/storage  efficiency.   The
standard, in fact, tends to be very free with the number of  bits
consumed.   For  example, field names are specified as free text,
rather than special terse codes.

     A general "memo" framework is  used.   That  is,  a  message
consists  of some information, in a rigid format, followed by the
main part of the message, which is text and whose format  is  not
specified  in this document.  The syntax of several fields of the
rigidly-formated  ("header")   section   is   defined   in   this
specification;  some of the header fields must be included in all
messages.  The syntax  which  distinguishes  between  headers  is
specified  separately  from  the  internal  syntax for particular
headers.  This separation is intended to allow  extremely  simple
parsers  to operate on the overall structure of messages, without
concern  for  the  detailed  structure  of  individual   headers.
Appendix B is provided to facilitate construction of these simple
parsers.  In addition to the fields specified in  this  document,
it  is  expected  that  other fields will gain common use.  User-
defined header fields allow systems to extend their functionality
while  maintaining  a uniform framework.  The approach is similar
to that of the TELNET protocol,  in  that  a  basic  standard  is
defined  which  includes  a  mechanism for (optionally) extending
itself.  As necessary, the authors of this document will regulate
the  publishing  of  specifications for these "extension-fields",
through the same mechanisms used to publish this document.

     Such a  framework  severely  constrains  document  tone  and
appearance  and  is  primarily useful for most intra-organization
communications  and  relatively   structured   inter-organization
communication.   A more robust environment might allow for multi-
font, multi-color, multi-dimension encoding  of  information.   A
less  robust  environment,  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
to paper-based communication, it is interesting to note that  the
Standard for the Format of Text Messages                        3
II. Framework

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.

Standard for the Format of Text Messages                        4
III. Syntax

                          III.  SYNTAX

     This  syntax  is  given  in  five  parts.   The  first  part
describes  the  notation  used  in the specification.  The second
part describes the base-level lexical analyzers  which  feed  the
higher-level  parser  described  in the succeeding sections.  The
third part gives a  general  syntax  for  messages  and  standard
header  fields;  and  the  fourth  part  specifies  the syntax of
addresses.  A final part  specifies  some  general  syntax  which
supports the other sections.


These specifications are made in an  augmented  Backus-Naur  Form
(BNF).  Differences  from  standard  BNF  involve  the  naming of
rules, the indication of repetition and of "local" alternatives.

1.  Rule naming

Angle brackets ("<", ">") are not used, in general.  The name  of
a   rule  is  simply  the  name  itself,  rather  than  "".
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.  Parentheses:  Local alternatives

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

3.  * construct:  Repetition

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


indicating at least  and at most  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.
Standard for the Format of Text Messages                        5
III. Syntax
  A. Notational Conventions

4.  element

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

5.  # construct:  Lists

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


indicating at least  and at most  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
element  is  required,  at  least  one  non-null  element must be

6.  [optional]

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

7.  ; Comments

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


1.  General Description

A message consists of headers and, optionally,  a  body  (i.e.  a
series of text lines).  The text part is just a sequence of lines
containing ASCII characters; it is separated from the headers  by
a null line (i.e., a line with nothing preceding the CRLF).

Standard for the Format of Text Messages                        6
III. Syntax
  B. Lexical Analysis

a.  Folding and unfolding of headers

    Each header item can be viewed as a single, logical  line  of
    ASCII characters.  For convenience, the field-body portion of
    this conceptual entity can  be  split  into  a  multiple-line
    representation  (i.e.,  "folded").   The general rule is that
    wherever there can be linear-white-space  (NOT  simply  LWSP-
    chars), a CRLF immediately followed by AT LEAST one LWSP-char
    can instead be inserted.  (However, a header's name  and  the
    following  colon  (":"),  which occur at the beginning of the
    header item, may NOT be folded onto multiple  lines.)   Thus,
    the single line

       To:  "Joe Dokes & J. Harvey" , JJV at BBN

    can be represented as

       To:  "Joe Dokes & J. Harvey" ,
            JJV at BBN


       To:  "Joe Dokes & J. Harvey"
        JJV at BBN


       To:  "Joe Dokes
        & J. Harvey" , JJV at BBN

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

b.  Structure of header fields

    Once header fields have been unfolded, they may be viewed  as
    being  composed  of  a  field-name followed by a colon (":"),
    followed by a field-body.  The field-name must be composed of
    printable  ASCII  characters  (i.e.,  characters  which  have
    values between 33.  and  126.,  decimal,  except  colon)  and
    LWSP-chars.   The  field-body  may  be  composed of any ASCII
    characters (other than  an  unquoted  CRLF,  which  has  been
    removed by unfolding).

    Certain field-bodies of  header  fields  may  be  interpreted
    according  to  an internal syntax which some systems may wish
    to parse.  These fields will be referred to  as  "structured"
    fields.    Examples   include  fields  containing  dates  and
Standard for the Format of Text Messages                        7
III. Syntax
  B. Lexical Analysis

    addresses.  Other fields, such as "Subject"  and  "Comments",
    are regarded simply as strings of text.

    NOTE:  Field-names, unstructured field bodies and  structured
    field  bodies  each  are  scanned  by  their own, INDEPENDENT
    "lexical" analyzer.

c.  Field-names

    To aid in the creation and reading of field-names,  the  free
    insertion  of  LWSP-chars  is  allowed in  reasonable places.

    Rather than obscuring the syntax specification for field-name
    with  the explicit syntax for these LWSP-chars, the existence
    of a "lexical" analyzer is assumed.  The analyzer  interprets
    the  text  which  comprises  the  field-name as a sequence of
    field-name atoms (fnatoms) separated by LWSP-chars

    Note that ONLY LWSP-chars may occur between the fnatoms of  a
    field-name and that CRLFs may NOT.  In addition, comments are
    NOT lexically recognized, as such, but parenthesized  strings
    are  legal  as  part  of  field-names.  These constraints are
    different from what is permissible  within  structured  field
    bodies.   In  particular,  this means that header field-names
    must wholly occur on the FIRST line of a folded  header  item
    and may NOT be split across two or more lines.

d.  Unstructured field bodies

    For  some  fields,  such  as  "Subject"  and  "Comments",  no
    structuring is assumed; and they are treated simply as texts,
    like those 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.

e.  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  in  reasonable  places.
    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 field bodies which
    are  simply unstructured strings of text, as described above.
    It provides an interpretation of the unfolded text comprising
    the  body  of  the  field  as  a sequence of lexical symbols.
    These symbols are:

            -  individual special characters
            -  quoted-strings
Standard for the Format of Text Messages                        8
III. Syntax
  B. Lexical Analysis

            -  comments
            -  atoms

    The first three of these symbols are self-delimiting.   Atoms
    are  not; they therefore are delimited by the self-delimiting
    symbols and by linear-white-space.  For the purposes  of  re-
    generating sequences of atoms and quoted-strings, exactly one
    SPACE is assumed to exist and should be  used  between  them.
    (Also,  in  Section  III.B.3.a,  note  the  rules  concerning
    treatment of multiple continguous LWSP-chars.)

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

            ":sysmail"@   Some-Host,
            Muhammed(I am   the greatest)Ali   at(the)WBA

    is analyzed into the following lexical symbols and types:

            ":sysmail"              quoted string
            @                       special
            Some-Host               atom
            ,                       special
            Muhammed                atom
            (I am   the greatest)   comment
            Ali                     atom
            at                      atom
            (the)                   comment
            WBA                     atom

    The cononical representations for the data in these addresses
    are  the  following  strings  (note that there is exactly one
    SPACE between words):

                :sysmail at Some-Host


                Muhammed Ali at WBA

2.  Formal Definitions

The first four rules, below, indicate a meta-syntax  for  fields,
without  regard to their particular type or internal syntax.  The
remaining rules define basic syntactic structures which are  used
by the rules in Sections III.C, III.D, and III.E.

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

field-name  =  fnatom *( LWSP-char [fnatom] )

Standard for the Format of Text Messages                        9
III. Syntax
  B. Lexical Analysis

fnatom      =  1*

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

field-body-contents = 

                                            ; (  Octal, Decimal.)
CHAR        =   ; (  0-177,  0.-127.)
ALPHA       =  
                                            ; (101-132, 65.- 90.)
                                            ; (141-172, 97.-122.)
DIGIT       =       ; ( 60- 71, 48.- 57.)
CTL         =            ; (    177,     127.)
CR          =  ;(     15,      13.)
LF          =        ; (     12,      10.)
SPACE       =           ; (     40,      32.)
HTAB        =  ; (     11,       9.)
<">         =      ; (     42,      34.)
CRLF        =  CR LF

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

specials    =  "(" / ")" / "<" / ">" / "@"  ; To use in a word,
            /  "," / ";" / ":" / "\" / <">  ;  word must be a
                                            ;  quoted-string.

delimiters  =  specials / comment / linear-white-space

text        =   atoms, specials,
                CR and/or bare LF, but NOT  ;  comments and
                including CRLF>             ;  quoted-strings are
                                            ;  NOT interpreted.

atom        =  1*

quoted-string = <"> *(qtext/quoted-pair) <">; Any number of qtext
                                            ;   chars or any
                                            ;   quoted char.

qtext       =        ; => may be folded
                and CR, and including

Standard for the Format of Text Messages                       10
III. Syntax
  B. Lexical Analysis

comment     =  "(" *(ctext / comment / quoted-pair) ")"
ctext       =   may be folded
                ")" and CR, and including

quoted-pair =  "\" CHAR

3.  Clarifications

a.  "White space"

    Remember that in field-names  and  structured  field  bodies,
    SURROUND ANY SYMBOL.  In all header fields, the only place in
    which at least one space is REQUIRED is at the  beginning  of
    continuation  lines  in a folded field.  When passing text to
    processes which do  not  interpret  text  according  to  this
    standard  (e.g.,  ARPANET FTP mail servers), then exactly one
    SPACE should be used in place of arbitrary linear-white-space
    and comment sequences.


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

    Note that  during  transmissions  across  the  ARPANET  using
    TELNET  NVT  connections,  data  must  conform  to TELNET NVT
    conventions (e.g., CR must be followed by either LF, making a
    CRLF, or , if the CR is to stand alone).

b.  Comments

    Comments are detected as such  only  within  field-bodies  of
    structured  fields.   A  comment  is  a  set  of TELNET ASCII
    characters, which is not within a quoted-string and which  is
    enclosed  in  matching parentheses; parentheses nest, so that
    if an unquoted left parenthesis occurs in a  comment  string,
    there  must  also  be  a  matching right parenthesis.  When a
    comment is used to act as the delimiter between a sequence of
    two  lexical  symbols,  such  as  two  atoms, it is lexically
    equivalent with one SPACE, for the purposes  of  regenerating
    the  sequence,  such as when passing the sequence onto an FTP
    mail server.

Standard for the Format of Text Messages                       11
III. Syntax
  B. Lexical Analysis

    In particular comments are NOT passed to the FTP  server,  as
    part  of  a MAIL or MLFL command, since comments are not part
    of the "formal" address.

    If a comment is to be "folded" onto multiple lines, then  the
    syntax for folding must be adhered to.  (See items III.B.1.a,
    above,  and  III.B.3.f,  below.)   Note  that  the   official
    semantics therefore do not "see" any unquoted CRLFs which are
    in comments, although particular parsing programs may wish to
    note  their  presence.   For  these  programs,  it  would  be
    reasonable to interpret a "CRLF LWSP-char" as  being  a  CRLF
    which  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.

c.  Delimiting and quoting characters

    The quote character (backslash) and characters which  delimit
    syntactic units are not, generally, to be taken as data which
    are part  of  the  delimited  or  quoted  unit(s).   The  one
    exception is SPACE.  In particular, the quotation-marks which
    define  a  quoted-string,  the  parentheses  which  define  a
    comment  and the backslash which quotes a following character
    are  NOT  part  of  the  quoted-string,  comment  or   quoted
    character.   A  quotation-mark  which  is  to  be  part  of a
    quoted-string, a parenthesis which is to be part of a comment
    and  a  backslash  which 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
    those which are not part of the alternate text  group  (i.e.,
    ctext or qtext).

    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 which 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 which delimit a quoted string and backslashes
    which  quote the following character should NOT accompany the
    quoted-string when the string is used with processes that  do
    not  interpret  data  according  to this specification (e.g.,
    ARPANET FTP mail servers).

Standard for the Format of Text Messages                       12
III. Syntax
  B. Lexical Analysis

d.  Quoted-strings

    Where   permitted  (i.e.,  in  words  in  structured  fields)
    quoted-strings   are   treated   as  a  single  symbol  (i.e.
    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 items III.B.1.a, above, and
    III.B.3.f,   below.)    Note   that  the  official  semantics
    therefore do not "see" any bare CRLFs which  are  in  quoted-
    strings,  although  particular  parsing  programs may wish to
    note  their  presence.   For  these  programs,  it  would  be
    reasonable  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 followed 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.

e.  Bracketing characters

    There are three types of brackets which must be well nested:

        o  Parentheses are used to indicate comments.

        o  Angle brackets ("<" and ">") are  generally  used
           to indicate the presence of at least one machine-
           usable code (e.g., delimiting mailboxes).

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

f.  Case independence of certain specials atoms

    Certain atoms, which are represented in the syntax as literal
    alphabetic  strings, can be represented in any combination of
    upper and lower case.  These are:

        -  field-name,
        -  "Include", "Postal" and equivalent atoms in a
           ":"":" address specification,
        -  "at", in a host-indicator,
        -  node,
        -  day-of-week,
        -  month, and
        -  zones.

    When matching an atom against one of these literals, case  is
    to  be ignored.  For example, the field-names "From", "FROM",
Standard for the Format of Text Messages                       13
III. Syntax
  B. Lexical Analysis

    "from", and even "FroM" should all  be  treated  identically.
    However,  the  case  shown in this specification is suggested
    for message-creating processes.  Note that, at the  level  of
    this  specification,  case  IS  relevant  to  other words and
    texts.  Also see Section IV.A.1.f, below.

g.  Folding long lines

    Each header item (field of the message) may be represented on
    exactly  one line consisting of the name of the field and its
    body; this is what the parser sees.  For readability,  it  is
    recommended  that the field-body portion of long header items
    be "folded" onto multiple lines of the actual header.  "Long"
    is  commonly  interpreted  to  mean  greater  than  65  or 72
    characters.  The former length is recommended as a limit, but
    it is not imposed by this standard.

h.  Backspace characters

    Backspace TELNET ASCII characters (ASCII BS, 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.


    NOTE:  Due to an artifact of the notational conventions,
           the  syntax indicates that, when present, "Date",
           "From", "Sender", and "Reply-To" fields  must  be
           in  a  particular order.  These header items must
           be unique (occur exactly once).   However  header
           fields, in fact, are NOT required to occur in any
           particular order, except that  the  message  body
           must  occur  AFTER  the headers.  For readability
           and ease of parsing  by  simple  systems,  it  is
           recommended  that  headers  be  sent in the order
           "Date", "From", "Subject", "Sender", "To",  "cc",
           etc.    This   specification   permits   multiple
           occurrences of  most  optional-fields.   However,
           their  interpretation  is not specified here, and
           their use is strongly 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  section  on  Lexical  Analysis  (section  II.B)
indicates how such long strings can be represented on more than
one line in the actual transmitted message.

Standard for the Format of Text Messages                       14
III. Syntax
  C. Messages

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

fields      =  date-field                   ; Creation time-stamp
               originator-fields            ;  & author id are
               *optional-field              ;  required: others
                                            ;  are all optional

originator-fields =
               (  "From"     ":" mailbox    ; Single author
                 ["Reply-To" ":" #address] )
            /  (  "From"     ":" 1#address  ; Multiple authors &
                  "Sender"   ":" mailbox    ;  may have non-mach-
                 ["Reply-To" ":" #address] );  ine addresses

date-field  =  "Date"       ":" date-time

optional-field  =
               "To"         ":" #address
            /  "cc"         ":" #address
            /  "bcc"        ":" #address    ; Blind carbon
            /  "Subject"    ":" *text
            /  "Comments"   ":" *text
            /  "Message-ID" ":" mach-id     ; Only one allowed
            /  "In-Reply-To"":" #(phrase / mach-id)
            /  "References" ":" #(phrase / mach-id)
            /  "Keywords"   ":" #phrase
            /  extension-field              ; To be defined in
                                            ;  supplemental
                                            ;  specifications
            /  user-defined-field           ; Must have unique
                                            ;  field-name & may
                                            ;  be pre-empted

extension-field = 

user-defined-field = 

Standard for the Format of Text Messages                       15
III. Syntax
  D. Addressee Items


address     =  host-phrase                  ; Machine mailbox
            / ( [phrase] "<" #address ">")  ; Individual / List
            / ( [phrase] ":" #address ";")  ; Group
            /  quoted-string                ; Arbitrary text
            / (":" ( "Include"              ; File, w/ addr list
                   / "Postal"               ; (U.S.) Postal addr
                   /  atom )                ; Extended data type
               ":" address)

mailbox     =  host-phrase /  (phrase mach-id)

mach-id     =  "<" host-phrase ">"          ; Contents must never
                                            ;  be modified!


host-phrase =  phrase  host-indicator       ; Basic address

host-indicator =  1*( ("at" / "@") node )   ; Right-most node is
                                            ;  at top of network
                                            ;  hierarchy; left-
                                            ;  most must be host

node        =  word / 1*DIGIT               ; Official host or
                                            ;  network name or
                                            ;  decimal address

date-time   =  [ day-of-week "," ] date time

day-of-week =  "Monday"    / "Mon"  / "Tuesday"   / "Tue"
            /  "Wednesday" / "Wed"  / "Thursday"  / "Thu"
            /  "Friday"    / "Fri"  / "Saturday"  / "Sat"
            /  "Sunday"    / "Sun"

date        =  1*2DIGIT ["-"] month         ; day month year
               ["-"] (2DIGIT /4DIGIT)       ;  e.g. 20 Aug [19]77

month       =  "January"   / "Jan"  / "February"  / "Feb"
            /  "March"     / "Mar"  / "April"     / "Apr"
            /  "May"                / "June"      / "Jun"
            /  "July"      / "Jul"  / "August"    / "Aug"
            /  "September" / "Sep"  / "October"   / "Oct"
            /  "November"  / "Nov"  / "December"  / "Dec"

Standard for the Format of Text Messages                       16
III. Syntax
  E. Supporting Constructs

time        =  hour zone                    ; ANSI and Military
                                            ;  (seconds optional)

hour        =  2DIGIT [":"] 2DIGIT [ [":"] 2DIGIT ]
                                            ; 0000[00] - 2359[59]

zone        = ( ["-"] ( "GMT"               ; Relative to GMT:
                                            ; North American
                 /  "NST" /                 ;  Newfoundland:-3:30
                 /  "AST" / "ADT"           ;  Atlantic: - 4/ - 3
                 /  "EST" / "EDT"           ;  Eastern:  - 5/ - 4
                 /  "CST" / "CDT"           ;  Central:  - 6/ - 5
                 /  "MST" / "MDT"           ;  Mountain: - 7/ - 6
                 /  "PST" / "PDT"           ;  Pacific:  - 8/ - 7
                 /  "YST" / "YDT"           ;  Yukon:    - 9/ - 8
                 /  "HST" / "HDT"           ;  Haw/Ala   -10/ - 9
                 /  "BST" / "BDT"           ;  Bering:   -11/ -10
                    1ALPHA       ))         ; Military: Z = GMT;
                                            ;  A:-1; (J not used)
                                            ;  M:-12; N:+1; Y:+12
            / ( ("+" / "-") 4DIGIT )        ; Local differential
                                            ;  hours/min. (HHMM)

phrase      =  1*word                       ; Sequence of words.
                                            ;  Separation seman-
                                            ;  tically = SPACE

word        =  atom / quoted-string

Standard for the Format of Text Messages                       17
IV. Semantics
 A. Address Fields

                         IV.  SEMANTICS


1.  General

a.  The phrase part of a host-phrase in an address  specification
    (i.e.,  the  host's name for the mailbox) is understood to be
    whatever the receiving FTP Server allows (for example,  TENEX
    systems  do  not  now understand addresses of the form "P. D.
    Q. Bach", but another system might).

    Note that a mailbox 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.

    An individual may have  several  mailboxes  and  a  group  of
    individuals  may wish to receive mail as a single unit (i.e.,
    a distribution list).  The second and third  alternatives  of
    an  address  list  (#address)  allow  naming  a collection of
    subordinate  addresses  list(s).   Recipient  mailboxes   are
    specified  within the bracketed part ("<" - ">" or ":" - ";")
    of such named lists.  The use of angle-brackets ("<", ">") is
    intended for the cases of individuals with multiple mailboxes
    and of special mailbox lists; it is not expected to be nested
    more  than  one level, although the specification allows such
    nesting.  The use of colon/semi-colon (":", ";") is  intended
    for  the  case  of  groups.   Groups  can be expected to nest
    (i.e., to  contain  subgroups).   For  both  individuals  and
    groups,  a  copy  of the transmitted message is to be sent to
    EACH mailbox  listed.   For  the  case  of  a  special  list,
    treatment of addresses is defined in the relevant subsections
    of this section.

b.  The inclusion of bare quoted-strings as addresses (i.e.,  the
    fourth  address-form  alternative)  is allowed as a syntactic
    convenience, but no semantics  are  defined  for  their  use.
    However,  it is reasonable, when replicating an address list,
    to replicate ALL of its members, including quoted-strings.

c.  ":Include:" specifications are used to refer to one  or  more
    locations  containing  stored  address  lists (#address).  If
    more than one location is referenced, the address part of the
    Include  phrase  must  be  a  list  (#address)  surrounded by
    angle-brackets, as per the "Individual / List" alternative of
. Constituent addresses must resolve to a host- Standard for the Format of Text Messages 18 IV. Semantics A. Address Fields phrase; only they have any meaning within this construct. The phrase part of indicated host-phrases should contain text which the referenced host can resolve to a file. This standard is not a protocol and so does not prescribe HOW data is to be retrieved from the file. However, the following requirements are made: o The file must be accessible through the local operating system interface (if it exists), given adequate user access rights; and o If a host has an FTP server and a user is able to retrieve any files from the host using that server, then the file must be accessible through FTP, using DEFAULT transfer settings, given adequate user access rights. It is intended that this mechanism allow programs to retrieve such lists automatically. The interpretation of such a file reference follows. This is not intended to imply any particular implementation scheme, but is presented to aid in understanding the notion of including file contents in address lists: o Elements of the address list part are alternates and the contents of ONLY ONE of them are to be included in the resultant address list. o The contents of the file indicated by a member host-phrase are treated as an address list and are inserted as an address list (#address) in the position of the path item in the syntax. That is, the TELNET ASCII characters specifying the entire Include
is replaced by the contents of one of the files to which the host- phrase(s), of the address list (#address), refers. Therefore, the contents of each file, indicated by an Include address, must be syntactically self-contained and must adhere to the full syntax prescribed herein for an address list. d. ":Postal:" specifications are used to indicate (U.S.) postal addresses, but can be treated the same as quoted-string addresses. To reference a list of postal addresses, the list must conform to the "Individual / List" alternative of
. The ":Include:" alternative also is valid. e. The "':' atom ':'" syntax is intended as a general mechanism for indicating specially data-typed addresses. As with extension-fields, the authors of this document will regulate Standard for the Format of Text Messages 19 IV. Semantics A. Address Fields the publishing of specifications for these extended data- types. In the absence of defined semantics, any occurrence of an address in this form may be treated as a quoted-string address. f. A node name must be THE official name of a network or a host, or else a decimal number indicating the Network address for that network or host, at the time the message is created. The USE OF NUMBERS IS STRONGLY DISCOURAGED and is permitted only due to the occasional necessity of bypassing local name tables. For the ARPANET, official names are maintained by the Network Information Center at SRI International, Menlo Park, California. Whenever a message might be transmitted or migrate to a host on another network, full hierarchical addresses must be specified. These are indicated as a series of words, separated by at-sign or "at" indications. The communication environment is assumed to consist of a collection of networks organized as independent "trees" except for connections between the root nodes. That is, only the roots can act as gateways between these independent networks. While other actual connections may exist, it is believed that presuming this type of organization will provide a reliable method for describing VALID, if not EFFICIENT, paths between hosts. A typical full mailbox specification might therefore look like: Friendly User @ hosta @ local-net1 @ major-netq In the simplest case, a mail-sending host should transmit the message to the node which is mentioned last (farthest to the right), strip off that node reference from the specification, and then pass the remaining host-phrase to the recipient host (in the ARPANET, its FTP server) for it to process. This treats the remaining portion of the host-indicator merely as the terminating part of the phrase. NOTE: When passing any portion of a host-indicator onto a process which does not interpret data according to this standard (e.g., ARPANET FTP servers), "@" must be used and not "at" and it must not be preceded or followed by any LWSP-chars. Using the above example, the following string would be passed to the major-netq gateway: Friendly User@hosta@local-net1 When the sending host has more knowledge of the network environment, then it should send the message along a more efficient path, making appropriate changes to the form of the host-phrase which it gives to the recipient host. Standard for the Format of Text Messages 20 IV. Semantics A. Address Fields To use the above specification as an example: If a sending hostb also were part of local-net1, then it could send the message directly to hosta and would give only the phrase "Friendly User" to hosta's mail-receiving program. If hostb were part of local-net2, along with hostc, and happened to know that hosta and hostc were part of another local-net, then hostb could send the message to hostc to the address "Friendly User@hosta". The phrase in a host-phrase is intended to be meaningful only to the indicated receiving host. To all other hosts, the phrase is to be treated as an uninterpreted string. No case transformations should be (automatically) performed on the phrase. The phrase is passed to the local host's mail sending program; it is the responsibility of the destination host's mail receiving (distribution) program to perform case mapping on this phrase, if required, to deliver the mail. 2. Originator Fields WARNING: The standard allows only a subset of the combinations possible with the From, Sender, and Reply-To fields. The limitation is intentional. a. 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 machine address, indicating the AGENT (person or process) entering the message. If this is NOT done, the "Sender" field MUST be present; if this IS done, the "Sender" field is optional. b. Sender This field contains the identity of the AGENT (person or process) who sends the message. It is intended for use when the sender is not the author of the message, 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 host-phrase includes a phrase 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 or process) responsible for sending the Standard for the Format of Text Messages 21 IV. Semantics A. Address Fields 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 phrase part of the host-phrase, 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. Since the critical function served by the "Sender" field is the identification of the agent responsible for sending mail and since computer programs cannot be held accountable for their behavior, is strongly recommended that when a computer program generates a message, the HUMAN who is responsible for that program be referenced as part of the "Sender" field host-phrase. c. 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 mailboxes 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, responses; responders should send their replies to the "Reply-To" mailbox(es) listed in the original message. 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. Reply-To fields are NOT required to contain any machine addresses (i.e., host-phrases). Note, however, that the absence of even one valid network address will tend to prevent software systems from automatically assisting users in conveniently responding to mail. NOTE: For systems which automatically generate address lists for replies to messages, the following recommendations are made: o The receiver, when replying to a message, should NEVER automatically include the "Sender" host-phrase in the reply's address list; o If the "Reply-To" field exists, then the reply should go ONLY to the addresses indicated in that field and not to the addresses indicated in the "From" field. Standard for the Format of Text Messages 22 IV. Semantics A. Address Fields (Extensive examples are provided in Section V.) This recommendation is intended only for originator-fields and is not intended to suggest that replies should not also be sent to the other recipients of this message. It is up to the respective mail handling programs to decide what additional facilities will be provided. 3. Receiver Fields a. To This field contains the identity of the primary recipients of the message. b. cc This field contains the identity of the secondary recipients of the message. b. 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 recipients. 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. B. REFERENCE SPECIFICATION FIELDS 1. Message-ID This field contains a unique identifier (the phrase) 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 each receive a new message identifier. 2. In-Reply-To The contents of this field identify previous correspondence which this message answers. Note that if message identifiers are used in this field, they must use the mach-id specification format. Standard for the Format of Text Messages 23 IV. Semantics B. Reference Specification Fields 3. References The contents of this field identify other correspondence which this message references. Note that if message identifiers are used, they must use the mach-id specification format. 4. Keywords This field contains keywords or phrases, separated by commas. C. OTHER FIELDS AND SYNTACTIC ITEMS 1. Subject The "Subject" field is intended to provide as much information as necessary to adequately summarize or indicate the nature of the message. 2. Comments Permits adding text comments onto the message without disturbing the contents of the message's body. 3. Extension-field A relatively limited number of common fields have been defined in this document. As network mail requirements dictate, additional fields may be standardized. The authors of this document will regulate the publishing of such definitions as extensions to the basic specification. 4. 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. Standard for the Format of Text Messages 24 IV. Semantics D. Dates D. DATES AND TIMES If included, day-of-week must be the day implied by the date specification. Time zone may be indicated in several ways. The military standard uses a single character for each zone. "Z" is Greenwhich Mean Time; "A" indicates one hour earlier, and "M" indicates 12 hours earlier; "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 GMT; the other uses common 3-character strings for indicating time zones in North America. Standard for the Format of Text Messages 25 V. Examples A. Addresses V. EXAMPLES A. ADDRESSES 1. Alfred E. Neuman 2. Neuman@BBN-TENEXA These two "Alfred E. Neuman" examples have identical semantics, as far as the operation of the local host's mail sending (distribution) program (also sometimes called its "mailer") and the remote host's FTP server are concerned. In the first example, the "Alfred E. Neuman" is ignored by the mailer, as "Neuman at BBN-TENEXA" completely specifies the recipient. The second example contains no superfluous information, and, again, "Neuman@BBN-TENEXA" is the intended recipient. 3. Al Neuman at BBN-TENEXA This is identical to "Al Neuman ". That is, the full phrase, "Al Neuman", is passed to the FTP server. Note that not all FTP servers accept multi-word identifiers; and some that do accept them will treat each word as a different addressee (in this case, attempting to send a copy of the message to "Al" and a copy to "Neuman"). 4. "George Lovell, Ted Hackle" 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, as "Shared-Mailbox at Office-1" completely specifies the destination mailbox. 4. Wilt (the Stilt) Chamberlain at NBA The "(the Stilt)" is a comment, which is NOT included in the destination mailbox address handed to the originating system's mailer. The address is the string "Wilt Chamberlain", with exactly one space between the first and second words. (The quotation marks are not included.) Standard for the Format of Text Messages 26 V. Examples B. Address Lists B. ADDRESS LISTS Gourmets: Pompous Person , Cooks: Childs at WGBH, Galloping Gourmet at ANT (Australian National Television);, Wine Lovers: Cheapie at Discount-Liquors, Port at Portugal;;, Jones at SEA This group list example points out the use of comments, the nesting of groups, and the mixing of addresses and groups. Note that the two consecutive semi-colons preceding "Jones at SEA" mean that Jones is NOT a member of the Gourmets group. C. ORIGINATOR ITEMS 1. Author-sent George Jones logs into his Host as "Jones". He sends mail himself. From: Jones at Host or From: George Jones 2. Secretary-sent George Jones logs in as Jones on his Host. His secretary, who logs in as Secy on Shost sends mail for him. Replies to the mail should go to George, of course. From: George Jones Sender: Secy at SHost 3. Shared directory or unrepresentative directory-name George Jones logs in as Group at Host. He sends mail himself; replies should go to the Group mailbox. From: George Jones Standard for the Format of Text Messages 27 V. Examples C. Originator Items 4. Secretary-sent, for user of shared directory George Jones' secretary sends mail for George in his capacity as a member of Group while logged in as Secy at Host. Replies should go to Group. From: George Jones Sender: Secy at Host 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). 5. Secretary acting as full agent of author George Jones asks his secretary (Secy at Host) to send a message for him in his capacity as Group. He wants his secretary to handle all replies. From: George Jones Sender: Secy at Host Reply-To: Secy at Host 6. Agent for user without online mailbox A non-ARPANET user friend of George's, Sarah, is visting. George's secretary sends some mail to a friend of Sarah in computer-land. Replies should go to George, whose mailbox is Jones at Host. From: Sarah Friendly Sender: Secy at Host Reply-To: Jones at Host 7. Sent by member of a committee George is a member of a committee. He wishes to have any replies to his message go to all committee members. From: George Jones Sender: Jones at Host Reply-To: Big-committee: Jones at Host, Smith at Other-Host, Doe at Somewhere-Else; Note that if George had not included himself in the enumeration of Big-committee, he would not have gotten an implicit reply; the presence of the "Reply-to" field SUPERSEDES the sending of a reply to the person named in the "From" field. Standard for the Format of Text Messages 28 V. Examples C. Originator Items 8. Example of INCORRECT use George desires a reply to go to his secretary; therefore his secretary leaves his mailbox address off the "From" field, leaving only his name, which is not, itself, a mailbox address. From: George Jones Sender: Secy at SHost THIS IS NOT PERMITTED. Replies are NEVER implicitly sent to the "Sender"; George's secretary should have used the "Reply-To" field, or the mail creating program should have forced the secretary to. 9. Agent for member of a committee George's secretary sends out a message which was authored jointly by all the members of the "Big-committee". From: Big-committee: Jones at Host, Smith at Other-Host, Doe at Somewhere-Else; Sender: Secy at SHost D. COMPLETE HEADERS 1. Minimum required: Date: 26 August 1976 1429-EDT From: Jones at Host 2. Using some of the additional fields: Date: 26 August 1976 1430-EDT From:George Jones Sender:Secy at SHOST To:Al Neuman at Mad-Host, Sam Irving at Other-Host Message-ID: Standard for the Format of Text Messages 29 V. Examples D. Complete Headers 3. About as complex as you're going to get: Date : 27 Aug 1976 0932-PDT From : Ken Davis Subject : Re: The Syntax in the RFC Sender : KSecy at Other-Host Reply-To : Sam Irving at Other-Host To : George Jones , Al Neuman at Mad-Host cc : Important folk: Tom Softwood , Sam Irving at Other-Host;, Standard Distribution::Include: standard.dist.3" at Tops-20-Host>, (The following Included Postal list is part of Standard Distribution.) :Postal::Include: Non-net-addrs@Other-host;, :Postal: "Sam Irving, P.O. Box 001, Las Vegas, Nevada" (So that he can stay apprised of the situation) 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: Special (action): This is a sample of multi-word field- names, using a range of characters. There could also be a field-name "Special (info)". Message-ID: <4231.629.XYzi-What at Other-Host> Standard for the Format of Text Messages 31 Appendix A. Alphabetical Listing of Syntax Rules APPENDIX A. ALPHABETICAL LISTING OF SYNTAX RULES address = host-phrase / quoted-string / (*phrase "<" #address ">" ) / (*phrase ":" #address ";" ) / (":" ("Include" / "Postal" / atom) ":" address) ALPHA = atom = 1* CHAR = comment = "(" *(ctext / comment / quoted-pair) ")" CR = CRLF = CR LF ctext = CTL = date = 1*2DIGIT ["-"] month ["-"] (2DIGIT /4DIGIT) date-field = "Date" ":" date-time date-time = [ day-of-week "," ] date time day-of-week = "Monday" / "Mon" / "Tuesday" / "Tue" / "Wednesday" / "Wed" / "Thursday" / "Thu" / "Friday" / "Fri" / "Saturday" / "Sat" / "Sunday" / "Sun" delimiters = specials / comment / linear-white-space DIGIT = extension-field = field = field-name ":" [ field-body ] CRLF fields = date-field originator-fields *optional-field field-body = field-body-contents [CRLF LWSP-char field-body] field-body-contents = field-name = fnatom *(LWSP-char [fnatom]) fnatom = 1* Standard for the Format of Text Messages 32 Appendix A. Alphabetical Listing of Syntax Rules host-indicator = 1*( ("at" / "@") node ) host-phrase = phrase host-indicator hour = 2DIGIT [":"] 2DIGIT [ [":"] 2DIGIT ] HTAB = LF = linear-white-space = 1*([CRLF] LWSP-char) LWSP-char = SPACE / HTAB mach-id = "<" host-phrase ">" mailbox = host-phrase / (phrase mach-id) message = fields *(CRLF *text) month = "January" / "Jan" / "February" / "Feb" / "March" / "Mar" / "April" / "Apr" / "May" / "June" / "Jun" / "July" / "Jul" / "August" / "Aug" / "September" / "Sep" / "October" / "Oct" / "November" / "Nov" / "December" / "Dec" node = word / 1*DIGIT optional-field = "To" ":" #address / "cc" ":" #address / "bcc" ":" #address / "Subject" ":" *text / "Comments" ":" *text / "Message-ID" ":" mach-id / "In-Reply-To"":" #(phrase / mach-id) / "References" ":" #(phrase / mach-id) / "Keywords" ":" #phrase / extension-field / user-defined-field originator-fields = ( "From" ":" mailbox ["Reply-To" ":" #address] ) / ( "From" ":" 1#address "Sender" ":" mailbox ["Reply-To" ":" #address] ) phrase = 1*word quoted-pair = "\" CHAR quoted-string = <"> *(qtext / quoted-pair) <"> qtext = , CR, or LF and including linear-white-space> SPACE = specials = "(" / ")" / "<" / ">" / "@"/ "," / ";" / ":" / "\" / <"> text = Standard for the Format of Text Messages 33 Appendix A. Alphabetical Listing of Syntax Rules time = hour zone user-defined-field = word = atom / quoted-string zone = ( ("+" / "-") 4DIGIT ) / ( ["-"] (1ALPHA / "GMT" / "NST" / "AST" / "ADT" / "EST" / "EDT" / "CST" / "CDT" / "MST" / "MDT" / "PST" / "PDT" / "YST" / "YDT" / "HST" / "HDT" / "BST" / "BDT" )) <"> = Standard for the Format of Text Messages 35 Appendix B. Simple Parsing B. SIMPLE 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: - Header fields from the message body, - Beginnings of fields from lines which continue fields, - Field-names from field-contents. The abbreviated set of syntactic rules which follows will suffice for this purpose. They describe a limited view of messages and are a subset of the syntactic rules provided in the main part of this specification. One small exception is that the contents of field-bodies consist only of text: SYNTAX: message = *field *(CRLF *text) field = field-name ":" [field-body] CRLF field-name = fnatom *( LWSP-char [fnatom] ) fnatom = 1* field-body = *text [CRLF LWSP-char field-body] 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), each separated by one or more SPACES or HTABS. A field-name MUST be contained on one line. Upper and lower case are not distinguished when comparing field-names. Standard for the Format of Text Messages 37 Bibliography BIBLIOGRAPHY ANSI. Representations of universal time, local time differentials, and United States time zone references for information interchange. ANSI X3.51-1975; American National Standards Institute: New York, 1975. Bhushan, A.K. The File Transfer Protocol. ARPANET Request for Comments, No. 354, Network Information Center No. 10596; Augmentation Research Center, Stanford Research Institute: Menlo Park, July 1972. Bhushan, A.K. Comments on the File Transfer Protocol. ARPANET Request for Comments, No. 385, Network Information Center No. 11357; Augmentation Research Center, Stanford Research Institute: Menlo Park, August 1972. 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; Augmentation Research Center, Stanford Research Institute: Menlo Park, September 1973. Feinler, E.J. and Postel, J.B. ARPANET Protocol Handbook. Network Information Center No. 7104; Augmentation Research Center, Stanford Research Institute: Menlo Park, April 1976. (NTIS AD A003890). McKenzie, A. File Transfer Protocol. ARPANET Request for Comments, No. 454, Network Information Center No. 14333; Augmentation Research Center, Stanford Research Institute: Menlo Park, February 1973. McKenzie, A. TELNET Protocol Specification. Network Information Center No. 18639; Augmentation Research Center, Stanford Research Institute: Menlo Park, August 1973. Myer, T.H. and Henderson, D.A. Message Transmission Protocol. ARPANET Request for Comments, No. 680, Network Information Center No. 32116; Augmentation Research Center, Stanford Research Institute: Menlo Park, 1975. Neigus, N. File Transfer Protocol. ARPANET Request for Comments, No. 542, Network Information Center No. 17759; Augmentation Research Center, Stanford Research Institute: Menlo Park, July 1973. Pogran, K., Vittal, J., Crocker, D. and Henderson, A. Proposed official standard for the format of ARPA network messages. Standard for the Format of Text Messages 38 Bibliography ARPANET Request for Comments, No. 724, Network Information Center No. 37435; Augmentation Research Center, Stanford Research Institute: Menlo Park, May 1977. Postel, J.B. Revised FTP Reply Codes. ARPANET Request for Comments, No. 640, Network Information Center No. 30843; Augmentation Research Center, Stanford Research Institute: Menlo Park, June 1974.