email virus protection

[Wayne Dawson]

Hello all,
   is there a consensus on what products and/or methods are the best to 
protect against email viruses, at the server level?
   Also, does anyone here have any experience with a product called Antivir?
   Here's our setup.  We will use Cyrus IMAP on Linux.  Incoming mail will 
go through a separate SMTP gateway machine (also Linux), and email will be 
retrieved by (1) Windows XP client machines on our LAN, and (2) a web based 
client that will probably be running on the same machine as the SMTP gateway.

Thanks for any suggestions you can give,
Wayne