On Mon, 14 May 2001, John Horne wrote:
> I would not have said 'illegal' simply because the RFC says 'SHOULD NOT' as
> opposed to 'MUST NOT' for the From: header. Although it specifies 'MUST NOT'
> for Resent headers. Secondly, I would rather reject a message which has an
> invalid (suspicious) From: header; why is an invalid (unresolvable)
> From: address being used?
Even for MUST NOT I would not use the word 'illegal'. The RFCs are not
legally binding documents. The intent of the RFCs is that, if you follow
their recommendations, you are most likely to be able to interwork
successfully with a large number of other hosts. MUST and SHOULD are
just different strengths of recommendation.
Of course, if you run a server on port 25 and have MX records pointing
to it, the rest of the Internet assumes that you do want to interwork,
and will complain to you if you violate the mail RFCs grossly.
However, having said that, you are perfectly entitled to reject any
message you want, for whatever reason you like, and an unresolvable
address in From: is a pretty good and sensible reason.
--
Philip Hazel University of Cambridge Computing Service,
ph10@??? Cambridge, England. Phone: +44 1223 334714.
