SMTP mail relay server for SPAM filtering

[Scott Henderson]

My company, like many, I'm sure, is wrestling with spam email. 
Currently we're handling it manually, creating blocks on our
Exchange server based on IP addresses.  We are not being given
any budget to solve this problem, but we do have a few spare
servers sitting around.  I'm thinking this may be an opportunity
to show the MS-based IT Dept what can be done with some Open
Source software.  I'd like suggestions on how to set up an SMTP
mail relay box and anti-spam software.  I have a year or so
experience with a few Linux distros on my desktop and laptop at
home, so I'm no wizard, but I can usually find my way around. 
Is this doable? We average around 6-700 SMTP emails per hour
during the day, and spike to maybe 1500 on occasion.  I want to
set the box up inside the DMZ, in front of the Exchange server,
and just have it relay to and from that box.  What distro?  What
software?  How to config?  Any HOWTOs on this or other resources? 
Thanks much! 

-----------------------------
Tired of Microsoft Windows?
Visit http://www.lycoris.com!