I installed a Windows 2007 Exchange server in to my 2003 environment this week. All went well apart from that the mail sending from the 2007 test mailboxes ended up in a queue called smtprelaytotirg. The error message given being 451 4.4.0 Primary Target IP Address Responded with (501 5.5.4 Auth Command Cancelled).
This queue is basically where 2007 is failing to deliver because it can’t route correctly.
The resolution in this case for me was easy. All the connectors were in place as they should be, but the transport for SMTP on the original master 2003 Exchange server had limited access to certain IP addresses.
I added the IP address for the new Exchange 2007 server and bang, 20 mins later the queue is empty.
Just a minor hurdle 🙂 Oh, the other one to watch out for is making sure it can resolve either by IP or FQDN for the SMTP server, it’ll fail on netbios or just a single name. Anyone still relying on WINS needs shot in the face with a screw driver.