A simple, configurable SMTP anti-spam filter: Greylists

This paper addresses methods for combating spam, focusing especially on those based on the economic motivations of unsolicited commercial e-mail. Considering the fact that to date no machine has passed the Turing test, well-known blacklist and whitelist solutions can be generalized by greylists. An outline of a simple SMTP anti-spam application following these ideas and running on a UNIX machine is offered. Some problems regarding the application are discussed, together with some of the results obtained after a two-month test period.