Bonnie, do you control the dns for the email server? If so, check out
http://en.wikipedia.org/wiki/Sender_Policy_Framework . We added a SPF record to our DNS and now receive at most one spoof reject per month because receiving servers see the e-mail is not really from us. More and more servers know to check for it.
"... They ne'er cared for us
yet: suffer us to famish, and their store-houses
crammed with grain; make edicts for usury, to
support usurers; repeal daily any wholesome act
established against the rich, and provide more
piercing statutes daily, to chain up and restrain
the poor. If the wars eat us not up, they will; and
there's all the love they bear us."
-- Shakespeare: Coriolanus, Act 1, scene 1
