http://www.amavis.org/
Can be setup with sendmail, postfix, etc. to automatically scan e-mail
attachments. I think they only support Sophos antivirus, but I could be
wrong. I tred Sophos and was impressed, but they never got back to me when I
requested a quote.

Search freshmeat for antivirus for other soultions.

--
Andy Zbikowski, Sys Admin   | (WEB) http://www.ltiflex.com
LTI Flexible Products, Inc. | (PH)  763-428-9119 (EX) 132
21801 Industrial Blvd       | (FX)  763-428-9126
Rogers, MN  55374           | (PCS) 612-306-6055