Antivirus (with exim+courier-imap+fetchmail)

[Thomas Halahan <tom@halahan.com>]

Hello,

I just set up a small mail server with exim+fetchmail+courier-imap.  In doing 
so, however, I seemed to have opened up a virus threat which was previously 
handled at the workstation where mail was downloaded straight from a pop3 
account on the net.  After some investigation is seems that I have the 
following options

1) Buy IMAP compatible virus software for the Windows work stations - although 
I cannot actually find any.

2) Buy a comercial email virus scanner, although very few seem to support exim 
which may force a switch to qmail or procmail.

3) Use a filter like amavis, and a commercial command line scanner which it 
supports.

4) Probably more configurations I had not thought of.

My budget is small, maybe $100.  

The following is the only HOWTO I have found

http://www.clues.ltd.uk/howto/debian-sa-fprot-HOWTO.txt

My question is therefore, what sort of suggestions people have to apply 
antivirus scanning?

Thanks, Tom