I have an internet-facing Exchange 2013 SP1 box (on Windows Server 2012 R2) and an Exchange 2010 box (on Windows Server 2008 R2). Both of these servers have their own AD forest, are both on the local network and no federation trusts have been established. I have exchange 2013 set up to route any mail with unresolved names to the Exchange 2010 server.
The issue I am having is that mail sits in the Submission queue on the Exchange 2013 server for some time (usually around 15 minutes)with the error "A local loop was detected" before successfully delivering to the Exchange 2010 mailbox.
The send connector on the Exchange 2013 server points to the local ip address of the Exchange 2010 server and the scope of the connector is "*".
I have also disabled Recipient Filtering on the Exchange 2013 server.
What am I missing?
Any help would be much appreciated.
Edit – Scrap the delivery after 15 minutes thing. Because the new Exchange 2013 server has not yet been implemented, I was temporarily changing the SMTP NAT address on the router to point to the Exchange 2013 server to test the routing, and then changing it back.
Best Answer
"The send connector on the Exchange 2013 server points to the local ip address of the Exchange 2010 server and the scope of the connector is "*"."
Don't do that. Exchange should never point to another Exchange server in the Send Connector. That is the cause of your problems. Send Connectors should only point to an external host. If you want email to go out through the other server, then remove the first connector and have the source set as the server to leave the org. Send Connectors are org settings, not server settings.
Are you really still on Exchange 2013 SP1? If so and the server hasn't been implemented, get it upgraded to the latest rollup before you do anything else.