Usually networks won't allow their computers to send email that "belongs" to
another network. That's called "relaying", and it's how a lot of
untrackable SPAM email is generated.
If that's the case, it's not a Vista problem at all!
Just ask your company's IT staff (or your telecom company) for help with
your e-mail's "outgoing SMTP server".
-Thomas H
"(e-mail address removed)"