Recommendation for "antivirus" software (MTA is qmail)

[David Wolfskill]

My boss, who persists in using a M$-based desktop, wants me to install
an "antivirus solution" on our mail server.  In fairness, he also wants
to reduce the expose to (and from) our customers (many of whom also run
such systems).

The MTA we currently use is qmail on a system running FreeBSD 4.8.
As far as I can tell, that is for its ease of integration with
vpopmail.  As far as this message is concerned, I am being agnostic
with respect to the choice of qmail for the MTA; it was made prior
to the start of my tenure here, and I am unwilling to make a change
if I believe that the result will not be worth the effort and
disruption.

A small bit of background:  my employer is a nascent ISP, with a fair
amount of emphasis on use of wireless (well, radio) technology.

It would be useful to be able to also get some spam-avoidance capability
along with this.  That said, several of our salient resources are limited.

A quick look around the Web shows some plausible-looking contenders;
what I seek are real-life experiences with these (or similar) products,
or other aspects that may not be immediately obvious from reading the
promotional material on the Web sites:

* qmail-scanner, clamav, and spamassassin
  http://clamav.elektrapro.com/doc/FreeBSD-HowTo/qmail-scanner-how-to.html

* Dr.Web for UNIX systems
  http://www.dials.ru/english/dsav_toolkit/drwebunix.htm
  [Also at http://www.advancedforce.com/antivirus/av_unixms.html ?]

* RAV AntiVirus
  http://www.ravantivirus.com/pages/isp.php

* Vexira Antivirus for Mail servers FreeBSD edition
  http://www.ti.com.pl/antivirus.php?s=vexira&d=products&w=details&pid=8

* AntiVir
  http://www.hbedv.com/

* Sophos PureMessage
  http://www.sophos.com/products/pm/

Each of the above (save the first) appears to be a commercial product.
We are open -- in principle -- to any solution, whether free or fee.

Thanks! (in advance)

Peace,
david
-- 
David H. Wolfskill                                 david at egation.com