Brian E Carpenter wrote:
I am disturbed that the messy situation of X- headers,
created by RFC 2822's silence on the subject, has not
been fixed.
As far as 2822 and 2822upd are concerned header fields
not specified in 2822 or 2822upd resp. are covered by
<optional-field> in section 3.6.8. This section does
not talk about field-names starting with "X-" or not.
See http://www.ietf.org/IESG/APPEALS/klensin-response.txt
for an example of the issues that this silence can create.
Gateways are always a difficult topic, and the 2822upd
syntax *minus* obs-* constructs is hopefully friendlier
to gateways than RFC 2822 *minus* obs-*.
Including obs-* constructs: 2822upd is slightly better
than before, a few RFC 822 #-cases not covered in 2822
are now accepted as obsolete, ASCII art with commas and
similar oddities.
I believe it would be appropriate to document that
although X- headers are widely used, they are not part
of the standard format and their treatment by Internet
MTAs MUST NOT be relied on, unless registered under
RFC 3864.
RFC 822 said that X- headers will *not* be standardized,
they are reserved for e-X-periments (my interpretation).
Do you propose that 2822upd should copy this rule from
RFC 822 ? Sorry, but I'm not sure what you are up to.
An MTA not supporting header X-foobar is not forced to
support header foobar only because it has no X-. As
far as 2822upd is concerned both are <optional-field>s.
Frank
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