It's not Exim-related, but it's mail-related, and exim-users is
the only mailing list I know that has people (notably Philip) who
grok mail-related RFCs.
My friend's domain (let's call it friends.dom) has a CNAME record
pointing to a host name under my domain, which has an MX record
to itself, and serves mail for both domains:
foo.friends.dom. IN CNAME bar.my.dom.
bar.my.dom. IN MX 10 bar.my.dom.
The machine (bar.my.dom) runs Exim with a config that handles
these domains differently, so local parts in one domain are not
necessarily valid in the other.
Versions of Postfix older than 2.0.0.1 (2002-12-09) seemed to
rewrite the recipient address if the domain part is a CNAME
record in the DNS, so people who wrote to friend@???
via a mail relay running older Postfix had the address rewritten
to friend@??? in the process. I only got that hint from
the reject log; the bounce generated by Postfix did not mention
the new adress at all.
I worked around this by changing CNAME records and creating
additional A records, but the question remains: was my setup
correct? Somebody suggested that there may be rules in the
sacred scriptures that discourage such play with CNAMES between
different domains and mail handling, but I can't recall anything
like that. Anybody?
And some more questions: do any MTAs except the older Postfix
rewrite recipient addresses based on CNAME records? And is there
anything in the RFCs that may be understood to permit such
behaviour? Honestly, it seems to me like a brain-dead idea
pulled out of a bodily orifice not normally mentioned in polite
circles, but I'm prepared to be shown the light if I'm mistaken.
Vadik.
--
Thoughts good! Slogans bad! Thoughts good! Slogans bad!
