spam/virus filter

[michal krajcirovic <konference@kraja.net>]

Hello,
from our current mailserver I want to build another server (which then 
set up an MX for domains), which will serve as an antispam / antivirus. 
I want through the mail, those who are out spam / viruses, and the rest 
forward, or to localize the subject *** SPAM ***, etc., which may then 
classify the existing mailserver.

It must be assumed that the role of "anti-spam gateway" to perform no 
one mailserver, but for several mailserver, it is therefore necessary to 
define something which he has subsequently served mails.

Does not someone with some experience in such a solution, possibly a 
reference to some instructions on how to do it? I search via Google, but 
apparently found nothing wrong and asked me not wise :-(

Thanks a lot.