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
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.
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
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 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.
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