This white paper explains why the answer to the question: "Is one anti-virus engine enough to protect the internal network from mass-mailing viruses, worms and other email-borne threats?" - is an emphatic "NO".

It also examines the need for multiple anti-virus engines to reduce the average response time to a virus outbreak, and thus reduce the chance of having your network infected. The use of multiple virus engines also enables security administrators to be vendor-independent when it comes to virus scanning, thereby able to use the best of breed virus engines available on the market.