I recently installed an Exchange 2007 server on my domain. The domain already had one Exchange 2003 server. I have migrated all of the mailboxes over to the new server and they can be accessed ok in Outlook. I am trying to decommission the 2003 server. In the process I think I created a situation where the two servers are not talking to each other, but yet the 2007 server seems to still want to rely on the 2003 server. After re-homing all resources (or so I thought) to the new server, I ran the uninstall for Exchange on the 2003 server, which appeared to go ok, but upon reboot Exchange was still present on the 2003 server. I have considered using the Exchange management tool on the 2003 server to remove that server from the organization, but I'm afraid that might make my situation even worse (though I shudder to think how).
On the 2007 server, I have set up the send connector under Organization Configuration / Hub Transport. It is set to specify the external domain name of the network and to use the 2007 server. My outbound messages are stuck in the queue with the error "421 4.4.0 Remote server response was not RFC conformant".
On the inbound side, I'm not receiving anything. I'm generating NDR's like such: "5.7.1 Unable to relay for email@example.com (in reply to RCPT TO command)". The inbound mails were originally showing up in the queue with the error "There is currently no route to the mailbox database." and also referencing the name of the 2003 server though I no longer have the exact text of that. Now the inbound ones are not showing in the queue at all.
I have set the default receipt connector to accept anonymous connections.
I'm suspecting that both problems may be coming from some hidden dependency the 2007 server has on the 2003 server.