Vista vs Email

(OK, it’s not really off-topic. But people in there are smart)

So.. we HAD to upgrade one computer to Vista, so we could test our software on it.

Of course, everything worked fine when it was an XP machine.

Now, (although nothing else has changed),the computer will recieve mail, but the blasted machine refuses to send email outside the domain. It does return this error message:

Server: ‘mail.*********.com ‘ Protcol: SMTP, Server Resonse: ‘550 5.7.2 unable to relay for mickster@****.net, port 25, secure (SSL) No, Server Error: 550, Error Number: 0x800ccc79

WE are useing the mail server program in Server 2003, and a simple POP 3 mail service.

Any ideas on how to get the mail sent?

Thanks!