Hey there.

I need all the help I can get on this:
I have to implement a working mail server solution for ~500 users in 5 different subdomains including decent spam and virus protection. My experience on mail servers is limited to a fall back host I have running for one of these domains that never really has to do much cause the main server worked pretty reliably until now.

I want to use the following software:
exim (with the acl and sa-exim patch)
clamav for virus scanning
spamassassin and
dcc for spam control
possibly procmail for further filtering

Apart from using exim as the MTA I'm open to other solutions.

The system will be a mail hub so the user's mailboxes don't reside on the same machine. I expect some 5000 mails/day or maybe more. What would the hardware requirements be when scanning for virii and spam is done at smtp rctp time so that anything that fails the scan is rejected right away before it even enters the system?
Can somebody point me to tested spamassassin configurations that minimize false positives? (I'm well aware that I will have to do some tweaking of the configuration but I just need something I can start up with.) Any experiences with virus scanners on a mail gateway? I'm not set on using clamav. I need a system for which new virus definitions are provided quickly cause our workstations are windows only and our users are exceptionally dumb in spotting virii in their inbox. Also has anyone experiences with dcc. That's the part I'm least familiar with but I thought it sounds like a neat idea. Any links to docs and shared experience with similar systems are greatly appreciated.

Thanks, demian