Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!sdd.hp.com!ucsd!ucbvax!TRANSARC.COM!Craig_Everhart
From: Craig_Everhart@TRANSARC.COM
Newsgroups: comp.mail.sendmail
Subject: Re: Local Configuration Error
Message-ID: <wayWTiX0BwwORNyX8k@transarc.com>
Date: 21 Sep 90 14:47:10 GMT
References: <6460@jhunix.HCF.JHU.EDU>
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Excerpts from netnews.comp.mail.sendmail: 20-Sep-90 Re: Local
Configuration Error Andy S Poling@jhunix.HCF (2399)

> Wrong, wrong, wrong.  I have a number of hosts that I would like to be able
> to "back each other up".  That is, if hostA is down, hostB is a secondary MX
> for hostA and will receive hostA's mail and queue it until hostA regains
> consciousness.  This approach takes the burden of retry-ing off of the
> far-away sender.

All the MX processing allows this to happen.

Let's say we have hosts A and B, and two MXs for A: one pointing to A
with preference 10, and one pointing to B with preference 20.  (MX(A) =
(10,A); MX(A) = (20,B).)  On host B (which is what we're concerned
with), all MXs with preference >= 20 will be discarded, but that will
nonetheless leave us with an MX pointing to domain A.  That's fine:
clearly, you need to do an address lookup on the targets for MX records.

All that Piet Beertema claims is that you shouldn't do address lookups
for host A just because you ran out of MX records, apparently a
debatable point.  The fact that the host name A is in both positions in
``MX(A) = (10,A)'' muddles the issue.

		Craig