Greylite is an implementation of a modified greylisting technology for fighting
SPAM on mailservers running qmail.

Greylite does not require patching qmail, it is self-contained because it uses
sqlite, it uses a technology that minimizes delivery delays and enables suspect
senders to be multiply rejected and never whitelisted.

Greylite is easy to setup and maintain, and it is small and fast. 

WWW: http://mij.oltrelinux.com/net/greylite/