If Linux is hardly affected by viruses, why do system administrators use anti-virus software on their Linux email servers? Because an anti-virus scanner on a mail server can serve as another level of defense for Microsoft Windows desktop users. Linux provides several server-based anti-virus applications, most of which can be configured to interact with a variety of messaging servers. Many use the actively developed ClamAV open source virus toolkit on the back end; others work with proprietary or commercial scanners. In this article we'll compare MailScanner and Anomy Sanitizer on a Sendmail messaging server.