Mailing List CGatePro@mail.stalker.com Message #94359
From: Uwe Baemayr <cgate@baemayr.com>
Subject: Multiple domains and reverse DNS
Date: Mon, 17 Mar 2008 23:57:27 -0500
To: CommuniGate Pro Discussions <CGatePro@mail.stalker.com>
X-Mailer: Pegasus Mail for Windows (4.41)
I have CommunigatePro v5.1.14 server on a multihomed Windows 2003 server that serves several domains.  Let's say the primary domain is 'main.net'. 

I have a subdomain on this server, 'subdomain.net', which sends email using an address separate from main.net.  So, for example:

  main.net sends and receives on 1.2.3.4
  subdomain.net sends and receives on 1.2.3.7

Reverse DNS for each domain points at the appropriate IP.

When main.net sends email on 1.2.3.4, all is well.  However, when subdomain.net sends email on 1.2.3.7, this appears in the received headers: 

Received: from main.net ([1.2.3.7] RDNS failed) by receiver.net with
          Microsoft SMTPSVC(6.0.3790.1830); Sat, 15 Mar 2008 00:15:41 -0500

A message actually sent from main.net instead of subdomain.net is ok:

Received: from main.net ([1.2.3.4]) by receiver.net with
          Microsoft SMTPSVC(6.0.3790.1830); Sat, 15 Mar 2008 00:17:43 -0500

In a brief exchange with support, I was told that the server always identifies itself using the primary licensed domain, so I gather that the receiving server did an reverse DNS check on 'main.net', rather than 'subdomain.net' and discovered the IP didn't match, hence the warning. 

Support also told me that there is no way to change how the server identifies itself, as it's a licensing issue.

So, how do you folks who serve multiple domains handle this situation?  I do have correct SPF records for each domain.  I do want to send from separate domains because the 'main.net' domain is listed in the senderbase reputation service and I don't want to risk having a subdomain that's not completely under my control damaging this sender's reputation.

Thanks!

--- Uwe
 
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