In the middle of an Exchange 2010 to 2010 migration and was testing mail flow. I had both servers listed under 'Source Server' in Organization Configuration, Hub Transport, Send Connectors.
I moved a user to the new server, then removed the old server from the Source Server list and sent a couple of test messages outside. I see emails queuing up on the old server. I was under the impression the source server was the server that would send out the emails...especially for a user that was on that server and database. Am I not understanding this correctly?
I have updated my firewall to use the IP of the new server for one-to-one NAT so PTR records match, etc.