I have looked at the threads and cannot resolve this common problem from those I have read relating to this so I am posting.
I have a Windows 2003 Server running POP3/SMTP mail servives (NO EXCHANGE, at least not at the moment). Inbound mail comes into the client fine. Outbound is the problem.
IF I do a test on the clent by going to Control Panel|Mail|E-mail Accounts|View or change existing e-mail accounts|Change|Test Account Settings, all tests are successful and I receive an e-mail stating so. I guess I assume that if I can run the tests then I am able to send out.
However, if I try to send to other domains, I get the "550 5.7.1 Unable to relay to domain" error. I need help in pinpointing how to solve this.