I thought I finally had Vista's windows mail set up correctly, it's receiving mail but won't send it. This is the administrator message I get;

This Message was undeliverable due to the following reason:

Your message was not delivered because the destination computer was
not found. Carefully check that it was spelled correctly and try
sending it again if there were any mistakes.

It is also possible that a network problem caused this situation,
so if you are sure the address is correct you might want to try to
send it again. If the problem continues, contact your friendly
system administrator.

Contact your ISP.