Good Idea, I think I'll give it a shot.
Volker also found a workaround using a product called SMTPAuth. You can read about his work at
http://vowe.net/archives/003031.html and get SMTPAuth at
http://netwinsite.com/dmail/smtpauth.htm.
Thanks to Henning Heinz for the reference.
I'll play with both (maybe) and let you know...