Mailing List Message #9352
From: Bill Cole <>
Subject: Re: Secondary mail server redux (no pun intended)
Date: Thu, 1 Nov 2001 07:37:08 -0500
To: SIMS Discussions <>
At 11:02 PM -0500 10/30/01, Listreader  imposed structure on a stream of electrons, yielding:
I poured through a number of postings over the past year to find the correct
way to set up a secondary mail server. But it does not seem to be right yet,
and I hope someone on  the list can point out the obvious mistake I made
somewhere along the line (which is why am so verbose with my setup details,
given below)

I am hosting multiple domains as well as having multiple servers, and that
may muddle the picture somewhat.
Anyway, I thought I had it figured out until I sent myself some mail today
when the primary mail server was acting flakey, and I got this bounce

Failed to deliver your message to
SMTP: DNS Routing Loop
The Domain Name System record for ''
points back to ''.
(rest of message, including header info, at end of this post, if it helps)

So here is what I have set up DNS and SIMS wise: Two backup mail servers.
One on a remote network, and one right next door to the main server. DNS as

DNS for
--------------------------------------------------------------        A   CNAME  A  A  MX 10  MX 20  MX 20

Never, under ANY circumstances, point an MX at a name that has a CNAME record. This will break in weird ways. Change the CNAME to an A pointing at, and you will eliminate a piece of the problem. (Yes, you can have as many A records pointing to an IP address as you like, it is totally harmless and extremely common. ) If you do that, make sure that the primary knows that it's name is also by adding a simple equate in the router.

On the other hand, you could totally eliminate the name and just point the primary MX records at instead. OR you could tell that server that its name is and put in an equate for in the router.

Bill Cole

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