not sending out mail


I had a SMTP problem where I would get an "Error (null)" message. The 10.02 update seemed to fix that problem. If I send a test message to myself, it seems to go through just fine. However, if I send an e-mail to any of the recipients in my Address Book, they do not get the e-mail. Any insights or clues as to what is happening?

I am experiencing this problem too. When I try to send a message to someone that is not a member of the host SMTP server, I get a message saying that the SMTP server does recognize the recipient. My mail server requires authorization to send mail but does not require that the recipient be a local user.

This does not happen in OS 9.1 or Outlook on my PC. I believe the mail app was working fine with the original OS X release. Seems something has happened in one of the upgrades. Currently I am running 10.0.2

Any ideas on what is causing this? I have seen simular posts in other forums but no resolution.