Qmail-Scanner, (also known as scan4virus) is an addon that enables a Qmail Email server to scan all gatewayed Email for certain characteristics. It is typically used for its anti-virus protection functions, in which case it is used in conjunction with commercial virus scanners. but also enables a site to react to Email (at a server/site level) that contains specific strings in particular headers, or particular attachment filenames or types (e.g. *.VBS attachments). It also can be used as an archiving tool for auditing or backup purposes. Qmail-Scanner is integrated into the mail server at a lower level than some other Unix-based virus scanners, resulting in better performance. It is capable of scanning not only locally sent/received Email, but also Email that crosses the server in a relay capacity. It also has SpamAssassin support.