[nmglug] can't send mail

[okeefe at cybermesa.com]

I have run into a problem sending mail either with T-Bird or Evolution. I can
send to myself but no one else and I get an error:
"An error occurred while sending mail. The mail server responded: 5.7.1
<address> Relaying denied. IP lookup failed [65.19.28.231]. Please verify that
your email address is correct in your mail preferences and try again."

I had installed Gnome-NetworkManager a couple days back and Spamato4Linux
also. Spamato just showed up as working today in T-Bird and I sent mail with
both these new apps running. I started getting these errors just a few hours
ago and had made no changes in configurations.
I'm running Ubuntu 6.06 on an Apple TiBook. I can send mail from my gmail
account or my ISP webmail service in a browser.
Any ideas?
Many thanks
brian
PS-I'll uninstall spamato and see if that helps, though it shouldn't since
Evolution isn't sending either.