Having trouble with a basic Exchange migration from SBS 2003 to Exchange 2010 running under Server 2008 R2.
Everything's installed. I can send mail in all directions from both servers, EXCEPT I can't send from 2010 to 2003. Messages sit in Exchange 2010 Server queue for unreachable domain.
I have created (then deleted and recreated) a pair of Routing Groups to go between the two servers.
Both servers have been restarted multiple times.
I've compared the routing groups, the SEND connectors and the RECEIVE connectors to other servers I've built and them match identically, but can't get mail to pass.
I've checked the 2003 Server to confirm that it's not routing all outbound mail to a smarthost, it's using DNS to directly route mail. I read in a few posts that could present an issue.
Any help would be appreciated!