Hello all,

I'm running Courier 0.37.2.20020131 and have a quick question about mail
routing.  One of my users got a bounce notification from Courier because
of an RFC 1035 violation.  I checked and, of course, the MX records were
mis-configured for the destination domain (one MX record returned an IP
instead of a name).  I happened to know a guy over at the organization
that controls one of the destination domain's nameservers, so I sent him a
note about the mis-configuration.  He responded:

--- begin friendly nameserver admin quotation ---
You're right.

RFC-1035, Section 3.3.9 does state that a hostname should be provided as a
response to an MX query.

On the other hand, your server should, per RFC-974 "remove irrelevant
RR's" and then "If the list of MX RRs is not empty, the mailer should try
to deliver the message to the MXs in order (lowest preference value tried
first)."  (Parentheses in original--MEE) Presumably that is what happened,
so you would have queued it for some period of time, then bounced if the
cost 10 machine never came available.
--- end friendly nameserver admin quotation ---


Now, the message did not queue, it bounced.  Courier said "no-go" and quit
because of the RFC 1035 error, even though the *other* MX record (which
also happened to be the *higher-priority* or less-expensive MX record) was
completely valid (verified via testmxlookup as well as dig).  I went ahead
and hard-coded a route in esmtproutes.  I don't even pretend to be
authoritative when it comes to these standards issues, once the discussion
moves past an obvious RFC violation.  So, with all trepidation, I simply
ask: shouldn't Courier trim the RR list as per RFC 974, eliminating
irrelevant RRs, and then try to deliver based on what's left after the
house cleaning?  Or, is my friend "the other hostmaster" off his rocker
and should I have bet him $5 on this issue?

Thanks,
Dan





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