Clam AntiVirus detect something like 24.000 signatures.
I saw somewhere on the web that a standard commercial AV detect about
80.000 signatures. So I decided to enable another AV on top of Clam.
I found a free tool at Panda  : 
http://www.pandasoftware.com/download/linux/linux.aspTo enable it, 
1) If you don't have amavis and clamAV,  you can get them at
http://www.dungog.net/sme/files/amavis-antivirus/2) modify  /etc/e-smith/templates/etc/amavis-ng/amavis.conf/conf
(or better, create a new one in template-custom) and  add 
    $OUT .= "virus-scanner = Panda\n";
just on top of 
    if ($clamemail eq 'on')
    {
      $OUT .= " virus-scanner = CLAMD\n";
      $powered .= 'CLAMD';
    } 
3) deploy the template : /sbin/e-smith/expand-template /etc/amavis-ng/amavis.conf
4) get the latest file  "Panda.pm" at  :
http://cvs.sourceforge.net/viewcvs.py/amavis/amavis-ng/AMAVIS/AV/and place it  here : /usr/lib/perl5/site_perl/5.6.1/AMAVIS/AV
Otherwhise, you will have a  "Message put into problems directory" ...problem
5)  You can test it using a test virus (be careful) at 
http://www.eicar.org/anti_virus_test_file.htm and send it via another linux machine
using the following command-line :  
#uuencode eicarcom2.zip eicarcom2.zip | mail you@yourdomain.net
That's it
hope it helps