linux mail gateway for viruses
 

i have redhat 8.0 linux box. it works as a file server and shares internet connection with NAT and squid.
nowadays lots of viruses come by emails. client antiviruses can catch most of them. but its not enaugh.
i want to use linux box as a email gateway, but not a real email gateway. i want to configure it to get emails from real email server for users. then sends them to real users. so it can check viruses before users download it. is it possible to do that? if its possible how can i do that?

thanks for your help..

I was looking into doing something similar myself but the project was halted - the best opensource mail antivirus products I could seem to find appeared to be:
http://clamav.elektrapro.com/
http://www.sng.ecs.soton.ac.uk/mailscanner/
http://freshmeat.net/projects/openprotect/
http://www.openantivirus.org/