Fix Outlook message delivery issues after Exchange 2003 upgrade

email only and use POP3 accounts for external email. Microsoft Outlook 2000 is our primary client. Exchange Server 5.5 allows us to compose a message and send it to both internal and external recipients. After the upgrade to Exchange Server 2003, Outlook does not allow this anymore. Messages to external recipients get returned as non-delivery reports. How can I adjust the settings in Outlook to allow the same behavior in Exchange Server 2003 as I once had when I was using Exchange Server 5.5?

A: It depends on what the non-delivery report (NDR) says. Most likely, this problem could be a domain name system (DNS) or mail-routing issue. I would consider looking at the Microsoft TechNet article on Microsoft Exchange Analyzers.

Specifically, check out the Exchange Server Troubleshooting Assistant. This Exchange tool executes a set of troubleshooting steps to identify the root cause of performance, mail flow, and database mounting issues.