From: Charles Lindsey (chl@clw.cs.man.ac.uk)
Date: Sun Apr 06 2003 - 12:45:05 CDT
The following summary shows all the differences between the usages in
RFC 2822 and in Usefor, as they stand in the current draft.
Differences between RFC 2822 and Usefor.
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1. Differences enforced syntactically.
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1.1 There is a REQUIRED SP (not even WSP) after the ':' in each header
(even if the header has no content).
1.2 An 'unstructured' MUST have at least one character. Thus the Subject
(for example) of an article cannot be empty.
1.3 In the References-header, there is an obligatory CFWS (currently
restricted to FWS) in between each msg-id.
NOTE: all the above were in RFC 1036.
1.4 The allowed characters in a header-name are restricted to ALPHA, DIGIT
and embedded '-'. However, agents SHOULD accept all printables except
SP and ':'.
1.5 Body lines are restricted to 998 characters plus CRLF (as in RFC
2822). However, all agents SHOULD, and relaying agents MUST, process
lines of arbitrary length.
1.6 RFC 2047 and RFC 2231 are fully integrated into the syntax. Thus
encoded-words are explicitly included within 'unstructured',
'ccontent' and 'phrase'. Moreover, it is the RFC 2231 version of
encoded-word that is used.
1.7 All the Content-* MIME headers are a REQUIRED part of the syntax.
1.8 All the "obsolete" syntax in RFC 2822 is NOT REQUIRED (though it MAY
be recognized). There is one small exception, see below.
1.9 In the Date-header, the obsolete "UT" and "GMT" forms of zone MUST be
recognized (because of their current widespread use), but MUST NOT be
generated.
1.10 BUG. We probabl;y should accept the (mis-named) "obsolete" syntax for
phrase from RFC 2822 which allows for 'John D. Smith' to remain
unquoted.
1.11 Message-ID
1.11.1 No CFWS allowed (only FWS, which in practice means only non-folded
WSP).
1.11.2 No quoted-pairs in msg-id, except for
'\\' and '\"' in id-left
'\[', '\]' and '\\' in id-right
1.11.3 No quoted-strings in id-left unless they contain one of the
"specials".
1.11.4 BUG. We need to forbid '>' entirely from inside a msg-id, even
within a quoted-string (to conform with RFC 1036).
1.11.5 All these restrictions on msg-id apply also to the References- and
Supersedes-headers.
2. Differences enforced by verbiage.
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2.1 The following MUST be accepted, but SHOULD NOT be generated (yet):
2.1.1 Comments, except after a mailbox, or at the end of a date-time.
2.2 The comment following a mailbox SHOULD be treated as meaningful (the
same as a phrase at the start of a mailbox). Nevertheless, using such
a comment for a "name" is deprecated (as in RFC 2822).
2.3 The content of the first line of a header MUST NOT consist of WSP only
(though such SHOULD be accepted). Observe that continuation lines
of headers also MUST NOT consist of WSP only, as in RFC 2822.
2.4 Headers with empty content are deprecated (but if present that SP
after the ':" is still required). Injecting agents SHOULD delete such
headers, but other agents MUST propagate them.
2.5 All agents MUST support header lines up to 998. The limit of 79
characters (as opposed to 78 in RFC 2822) is purely advisory - there
is no SHOULD about it.
2.6 Relaying agents MUST NOT refold headers in transit.
2.7 There must not be more than one header with a given header-name,
except where explicitly sanctioned by the appropriate standard. In
particular, there MUST NOT be more than one Keywords-header.
2.8 The length of a msg-id MUST NOT exceed 250 octets.
2.9 The body of an article SHOULD NOT be empty.
2.10 A Subject-header MUST NOT begin with "Re: Re: ".
3. Rules specific to Netnews headers.
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3.1 All headers have MIME-style extension-parameters, with x-attributes
or to be defined in future standards. Some have explicit parameters
defined in this standard. However, this does not apply to headers
which are taken from RFC 2822 or other mail standards, nor to the
Mail-Copies-To, Complaints-to and Supersedes-header defined in this
standard. Nevertheless, such parameters SHOULD be recognized (and
ignored) in all headers.
3.2 Comments (but not FWS) are forbidden in the Message-ID-, Newsgroups-,
Distribution- and Path- and Followup-To-headers.
3.3 The following MUST be accepted, but SHOULD NOT be generated (yet):
3.3.1 MIME-style parameters in headers defined prior to this standard.
3.3.2 WSP and folding in Newsgroup- and Followup-To-headers.
Charles H. Lindsey ---------At Home, doing my own thing------------------------
Tel: +44 161 436 6131 Fax: +44 161 436 6133 Web: http://www.cs.man.ac.uk/~chl
Email: chl@clw.cs.man.ac.uk Snail: 5 Clerewood Ave, CHEADLE, SK8 3JU, U.K.
PGP: 2C15F1A9 Fingerprint: 73 6D C2 51 93 A0 01 E7 65 E8 64 7E 14 A4 AB A5