From mboxrd@z Thu Jan  1 00:00:00 1970
Message-ID: <afcb163908214423c69212f9647e0cb0@coraid.com>
From: erik quanstrom <quanstro@coraid.com>
Date: Tue, 16 Jan 2007 12:01:35 -0500
To: mteege@gmail.com, 9fans@cse.psu.edu
Subject: Re: [9fans] $smtp dns failure
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the behaviour is not correct. rfc 2821 (section 5) says

  The lookup first attempts to locate an MX
   record associated with the name.  If a CNAME record is found instead,
   the resulting name is processed as if it were the initial name.  If
   no MX records are found, but an A RR is found, the A RR is treated as
   if it was associated with an implicit MX RR, with a preference of 0,
   pointing to that host.  If one or more MX RRs are found for a given
   name, SMTP systems MUST NOT utilize any A RRs associated with that
   name unless they are located using the MX RRs; the "implicit MX" rule
   above applies only if there are no MX records present.  If MX records
   are present, but none of them are usable, this situation MUST be
   reported as an error.

- erik