Mailing List SIMS@mail.stalker.com Message #9352
From: Bill Cole <listbill@scconsult.com>
Subject: Re: Secondary mail server redux (no pun intended)
Date: Thu, 1 Nov 2001 07:37:08 -0500
To: SIMS Discussions <SIMS@mail.stalker.com>
At 11:02 PM -0500 10/30/01, Listreader  imposed structure on a stream of electrons, yielding:
Hi,
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
message:

------------------------------------------------------------
Failed to deliver your message to kevin@manuex.com.smtp:
SMTP: DNS Routing Loop
The Domain Name System record for 'manuex.com.smtp'
points back to 'mail2.manuex.com'.
------------------------------------------------------------
(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
follows:

--------------------------------------------------------------
DNS for manuex.com
--------------------------------------------------------------
manuex.com        A      66.92.77.165
mail.manuex.com   CNAME  manuex.com
mail2.manuex.com  A      65.84.187.144
mail3.manuex.com  A      66.92.77.164

manuex.com  MX 10  mail.manuex.com
manuex.com  MX 20  mail2.manuex.com
manuex.com  MX 20  mail3.manuex.com
--------------------------------------------------------------

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 66.92.77.165, 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 mail.manuex.com by adding a simple equate in the router.

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


--
Bill Cole
bill@scconsult.com

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