You didn't post what Linux distro you use, so I am going to assume it's a RedHat or CentOS version.
What I recommend is that you install the following:
1. RulesDuJour - an addon to Spamassassin with lots of great rulesets which greatly enhance the effectiveness of SA.
http://www.exit0.us/index.php?pagename=RulesDuJour
2. Yum - an update program similar to up2date, apt-get. Configure the /etc/yum.conf to use ARTs channels
3. DrWeb AV - dump this lame and very buggy expensive POS.
4. ClamAV - great AV scanning software, can setup cronjob to autoupdate daily (use yum/ART)
5. F-Prot - can also be used at same time as clamav, 2 layers is better than 1. Cronjob the update script.
6. Qmail-scanner - a sofware package which automates coordination of email scanning, can be used with multiple AntiVirus packages, Spamassassin, and perl-scan. I use ART's (atomicrocketturtle.com) yum repository for this.
Qmail-scanner has a number of SA config options which really make things easy. Per site/server, per user, drop if score above x.x, and more.
7. mod_security - Highly recommend installing this as a minimum to server hardening. Also cronjob the update script.
8. Server hardening - see ART's ASL (Atomic Secured Linux) which includes mod_security, but goes way beyond. Many admins don't go this far, but for the small yearly fee it can be a lifesaver down the road. Too many script kiddies out there....
It may seem like a lot to do, but these simple things will make your admin life so much better.