Are you acting as your own ISP or do you have a commercial ISP?
I use Front Range Internet, a local ISP operating north of Denver and they have MailAmory which
scans all incoming emails for trojans, worms, and viruses and captures them. In 7 years I have
NEVER been damaged by a virus of any kind. Back in 1999-2000 or so, I got viruses but was
using Netscape 4.x as a mail reader and most of the worms exploited problems in Microsoft
Outlook or Outlook express which I avoid using for that reason. Netscape didn't recognize the
security hole they were trying to exploit.
Mail Armory is available for other service providers. See http://www.mailarmory.com