I am unable to route email from an Exchange 2010 box to my Exchange 2003 server. Messages sit in the queue on the 2010 server, and I finally get an error 421 4.2.2 and something about a Socket error. I have not been able to get the exact message because it only appears when the queue goes into Retry mode (as opposed to Active) which is not very often. Users on the Exchange 2003 server can send to a user on Exchange 2010. Everyone can send and receive Internet email (Exchange 2003 is receiving inbound SMTP). The issue is strictly one way from Exchange 2010 to Exchange 2003.
I worked with Microsoft Tech support yesterday, but they have not been able to solve. I am waiting for a call back from their Level 2 support.
-Exchange 2010 running on Windows 2008 R2 configured as DC
-Exchange 2003 running Windows 2003 R2, configured as DC
-There are two other Exchange 2003 servers in the organization, not being used, will be retired