Problem: Got the error below from two separate exchange servers on different sites:
This message hasn’t been delivered yet. Delivery will continue to be attempted.
The server will keep trying to deliver this message for the next 1 days, 19 hours and 53 minutes. You’ll be notified if the message can’t be delivered by that time.
Site 1: Retired the Exchange 2003 server and started to receive this error within 24 hours or it being retired. This told me that the Exchange 2003 server was still acting as the outgoing SMTP server.
Site 2: Already had itâ€™s Exchange 2003 server retired and email had been flowing properly for a while nowâ€¦
Turns out on both sites the smart host wasnâ€™t configured properly.
Site 1: Had to create a new send connector and configure it to send email to the designated smart host in our organization. Be default a send connector was installed during the initial Exchange 2010 installation but I could not specify the source server on that one. Which told me this connector was specific to the co-existence with the Exchange 2003 server. Once I created the new connector with the proper source server, all was well.
Site 2: This site had the 2nd send connector but didnâ€™t have the smart host configured. It was set to send mail by using DNS. Once I set the smart host, mail began to flow properly.