For basic installation instructions, see Jon Atkins' README, also in this directory. The chief difference between my version and his, is that this one requires a MySQL database in order to work; it's easy to set up. Here's an example to get you started: (as of version 0.2) CREATE DATABASE greylist; USE greylist; GRANT ALL ON greylist.* TO greylist@localhost IDENTIFIED BY ''; DROP TABLE IF EXISTS `ips`; CREATE TABLE `ips` ( `ip_addr` text, `atime` datetime default NULL, `mtime` datetime default NULL, `times_seen` int(11) default '0' ) Then set it up as you would Jon's version. This script also records for statistics purposes the number of times it's seen every IP.