Routing Group Connector - Loop condition 2010

Today I’ve been troubleshooting a looping condition on a Exchange 2003 -> 2010 transition. The mail flow from Exchange 2010 -> 2003 is working fine, and with a new SMTP connector for internet mail the Exch2010 is able to send to the internet.

But one thing does not work, and that is mail flow between the Exc2003 and Exc2010. No NDRs, nothing is reported back from the system, but the mails are located in the “Messages queued for deferred delivery”queue. When the SMTP service is stopped, I receive a NDR for the messages saying it’s a loop:

Your message did not reach some or all of the intended recipients.
Subject: Test 11
Sent: 5/01/2010 3:34 PM
The following recipient(s) could not be reached:
user@domainname.com on 5/01/2010 3:34 PM
A configuration error in the e-mail system caused the message to bounce between two servers or to be forwarded between two recipients. Contact your administrator.


The exchange 2003 organization does not have other routing group connectors, and is not using Smarthost for outgoing emails. The Exc2010 RoutingGroupConnector created during install has been deleted and recreated to see if that did the trick, but it didn’t.

It turns out that the Exc2003 cluster had 2 SMTP virtual servers, where as one was stopped due to some old errors, and the on the routinggroupconnector this was the SMTP server used. I could not find any powershell parameters to define a different SMTP virtual server, so I had to use ADSIEDit to change the default SMTP virtual server on the connector. Thanks to Winroute for giving me a red cross on the RoutingConnector, and sending me in the direction of multiple SMTP servers.

After changing this and wait for the Exchange to pick up the config from AD, mail flow is now working both ways between Exc2003<->Exch2010.