Virus Protection for Linux mail servers

[Mark Knecht <mknecht controlnet com>]

Hi there,
   Can anyone provide information on what is available for Linux based email
servers? 

   The organization here is basically Win NT based, but we'd like to dump
our Exchange Server and go with one of the Linux based email servers. How do
I eliminate viruses at the server so that I'm not depending totally on each
and every workstation being up to date? (Workstations will continue to have
virus protection anyway...)

Thanks,
Mark