Dann,
You can quickly block a sender within the SmarterMail web interface by right clicking the message, selecting Actions -> Blocked sender. This will add an entry to an internal blocked senders list content filter, by default this outright deletes the messages when they are from a blocked sender. Your end users can modify this to send to a junk e-mail folder, and a variety of other actions.
You can also leverage the bayesian filtering spam check that learns based on when your users flag messages as spam\not spam.
Von See
Technical Support Supervisor
SmarterTools Inc.
(877) 357-6278
www.smartertools.com