[Spambayes] Spam overload

[Russell, Stephen]

Dear experts,
We are a school system with 1100 faculty and 7000 student accounts on a
Win2000 server with Exchange 5.5 SP3.  We are in spam overload and are in
desperate need of help.  What can I do to stop this onslaught of unwanted
mail and still be able to afford to maintain our network?  I am a department
of one and I need a product that is simple to use, doesn't require massive
amounts of admin time, and doesn't cost an arm and a leg.  I don't like the
idea of subscribing to an online service with a yearly fee and would prefer
that the app sit on the Exchange box.
I have done a lot of research and it has brought me to you.  By reading your
site I can see you guys are at the forefront of this endeavor to stop spam
and thought that you could point me in the right direction.
 
Any ideas?
 
Thanks,
Stephen Russell