rfc2822.txt

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ccontent        =       ctext / quoted-pair / comment

comment         =       "(" *([FWS] ccontent) [FWS] ")"

CFWS            =       *([FWS] comment) (([FWS] comment) / FWS)

   Throughout this standard, where FWS (the folding white space token)
   appears, it indicates a place where header folding, as discussed in
   section 2.2.3, may take place.  Wherever header folding appears in a
   message (that is, a header field body containing a CRLF followed by
   any WSP), header unfolding (removal of the CRLF) is performed before
   any further lexical analysis is performed on that header field
   according to this standard.  That is to say, any CRLF that appears in
   FWS is semantically "invisible."

   A comment is normally used in a structured field body to provide some
   human readable informational text.  Since a comment is allowed to
   contain FWS, folding is permitted within the comment.  Also note that
   since quoted-pair is allowed in a comment, the parentheses and



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   backslash characters may appear in a comment so long as they appear
   as a quoted-pair.  Semantically, the enclosing parentheses are not
   part of the comment; the comment is what is contained between the two
   parentheses.  As stated earlier, the "\" in any quoted-pair and the
   CRLF in any FWS that appears within the comment are semantically
   "invisible" and therefore not part of the comment either.

   Runs of FWS, comment or CFWS that occur between lexical tokens in a
   structured field header are semantically interpreted as a single
   space character.

3.2.4. Atom

   Several productions in structured header field bodies are simply
   strings of certain basic characters.  Such productions are called
   atoms.

   Some of the structured header field bodies also allow the period
   character (".", ASCII value 46) within runs of atext.  An additional
   "dot-atom" token is defined for those purposes.

atext           =       ALPHA / DIGIT / ; Any character except controls,
                        "!" / "#" /     ;  SP, and specials.
                        "$" / "%" /     ;  Used for atoms
                        "&" / "'" /
                        "*" / "+" /
                        "-" / "/" /
                        "=" / "?" /
                        "^" / "_" /
                        "`" / "{" /
                        "|" / "}" /
                        "~"

atom            =       [CFWS] 1*atext [CFWS]

dot-atom        =       [CFWS] dot-atom-text [CFWS]

dot-atom-text   =       1*atext *("." 1*atext)

   Both atom and dot-atom are interpreted as a single unit, comprised of
   the string of characters that make it up.  Semantically, the optional
   comments and FWS surrounding the rest of the characters are not part
   of the atom; the atom is only the run of atext characters in an atom,
   or the atext and "." characters in a dot-atom.







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3.2.5. Quoted strings

   Strings of characters that include characters other than those
   allowed in atoms may be represented in a quoted string format, where
   the characters are surrounded by quote (DQUOTE, ASCII value 34)
   characters.

qtext           =       NO-WS-CTL /     ; Non white space controls

                        %d33 /          ; The rest of the US-ASCII
                        %d35-91 /       ;  characters not including "\"
                        %d93-126        ;  or the quote character

qcontent        =       qtext / quoted-pair

quoted-string   =       [CFWS]
                        DQUOTE *([FWS] qcontent) [FWS] DQUOTE
                        [CFWS]

   A quoted-string is treated as a unit.  That is, quoted-string is
   identical to atom, semantically.  Since a quoted-string is allowed to
   contain FWS, folding is permitted.  Also note that since quoted-pair
   is allowed in a quoted-string, the quote and backslash characters may
   appear in a quoted-string so long as they appear as a quoted-pair.

   Semantically, neither the optional CFWS outside of the quote
   characters nor the quote characters themselves are part of the
   quoted-string; the quoted-string is what is contained between the two
   quote characters.  As stated earlier, the "\" in any quoted-pair and
   the CRLF in any FWS/CFWS that appears within the quoted-string are
   semantically "invisible" and therefore not part of the quoted-string
   either.

3.2.6. Miscellaneous tokens

   Three additional tokens are defined, word and phrase for combinations
   of atoms and/or quoted-strings, and unstructured for use in
   unstructured header fields and in some places within structured
   header fields.

word            =       atom / quoted-string

phrase          =       1*word / obs-phrase








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utext           =       NO-WS-CTL /     ; Non white space controls
                        %d33-126 /      ; The rest of US-ASCII
                        obs-utext

unstructured    =       *([FWS] utext) [FWS]

3.3. Date and Time Specification

   Date and time occur in several header fields.  This section specifies
   the syntax for a full date and time specification.  Though folding
   white space is permitted throughout the date-time specification, it
   is RECOMMENDED that a single space be used in each place that FWS
   appears (whether it is required or optional); some older
   implementations may not interpret other occurrences of folding white
   space correctly.

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

day-of-week     =       ([FWS] day-name) / obs-day-of-week

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

date            =       day month year

year            =       4*DIGIT / obs-year

month           =       (FWS month-name FWS) / obs-month

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

day             =       ([FWS] 1*2DIGIT) / obs-day

time            =       time-of-day FWS zone

time-of-day     =       hour ":" minute [ ":" second ]

hour            =       2DIGIT / obs-hour

minute          =       2DIGIT / obs-minute

second          =       2DIGIT / obs-second

zone            =       (( "+" / "-" ) 4DIGIT) / obs-zone





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   The day is the numeric day of the month.  The year is any numeric
   year 1900 or later.

   The time-of-day specifies the number of hours, minutes, and
   optionally seconds since midnight of the date indicated.

   The date and time-of-day SHOULD express local time.

   The zone specifies the offset from Coordinated Universal Time (UTC,
   formerly referred to as "Greenwich Mean Time") that the date and
   time-of-day represent.  The "+" or "-" indicates whether the
   time-of-day is ahead of (i.e., east of) or behind (i.e., west of)
   Universal Time.  The first two digits indicate the number of hours
   difference from Universal Time, and the last two digits indicate the
   number of minutes difference from Universal Time.  (Hence, +hhmm
   means +(hh * 60 + mm) minutes, and -hhmm means -(hh * 60 + mm)
   minutes).  The form "+0000" SHOULD be used to indicate a time zone at
   Universal Time.  Though "-0000" also indicates Universal Time, it is
   used to indicate that the time was generated on a system that may be
   in a local time zone other than Universal Time and therefore
   indicates that the date-time contains no information about the local
   time zone.

   A date-time specification MUST be semantically valid.  That is, the
   day-of-the-week (if included) MUST be the day implied by the date,
   the numeric day-of-month MUST be between 1 and the number of days
   allowed for the specified month (in the specified year), the
   time-of-day MUST be in the range 00:00:00 through 23:59:60 (the
   number of seconds allowing for a leap second; see [STD12]), and the
   zone MUST be within the range -9959 through +9959.

3.4. Address Specification

   Addresses occur in several message header fields to indicate senders
   and recipients of messages.  An address may either be an individual
   mailbox, or a group of mailboxes.

address         =       mailbox / group

mailbox         =       name-addr / addr-spec

name-addr       =       [display-name] angle-addr

angle-addr      =       [CFWS] "<" addr-spec ">" [CFWS] / obs-angle-addr

group           =       display-name ":" [mailbox-list / CFWS] ";"
                        [CFWS]




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display-name    =       phrase

mailbox-list    =       (mailbox *("," mailbox)) / obs-mbox-list

address-list    =       (address *("," address)) / obs-addr-list

   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 a printer and deliver the output to the
   addressee's desk.  Normally, a mailbox is comprised of two parts: (1)
   an optional display name that indicates the name of the recipient
   (which could be a person or a system) that could be displayed to the
   user of a mail application, and (2) an addr-spec address enclosed in
   angle brackets ("<" and ">").  There is also an alternate simple form
   of a mailbox where the addr-spec address appears alone, without the
   recipient's name or the angle brackets.  The Internet addr-spec
   address is described in section 3.4.1.

   Note: Some legacy implementations used the simple form where the
   addr-spec appears without the angle brackets, but included the name
   of the recipient in parentheses as a comment following the addr-spec.
   Since the meaning of the information in a comment is unspecified,
   implementations SHOULD use the full name-addr form of the mailbox,
   instead of the legacy form, to specify the display name associated
   with a mailbox.  Also, because some legacy implementations interpret
   the comment, comments generally SHOULD NOT be used in address fields
   to avoid confusing such implementations.

   When it is desirable to treat several mailboxes as a single unit
   (i.e., in a distribution list), the group construct can be used.  The
   group construct allows the sender to indicate a named group of
   recipients. This is done by giving a display name for the group,
   followed by a colon, followed by a comma separated list of any number
   of mailboxes (including zero and one), and ending with a semicolon.
   Because the list of mailboxes can be empty, using the group construct
   is also a simple way to communicate to recipients that the message
   was sent to one or more named sets of recipients, without actually
   providing the individual mailbox address for each of those
   recipients.

3.4.1. Addr-spec specification

   An addr-spec is a specific Internet identifier that contains a
   locally interpreted string followed by the at-sign character ("@",
   ASCII value 64) followed by an Internet domain.  The locally