Policyd v2 (codenamed "cluebringer") is a multi-platform policy server for popular MTAs. This policy daemon is designed mostly for large scale mail hosting environments. The main goal is to implement as many spam combating and email compliance features as possible while at the same time maintaining the portability, stability and performance required for mission critical email hosting of today. Most of the ideas and methods implemented in Policyd v2 stem from Policyd v1 as well as the authors' long time involvement in large scale mail hosting industry.
Old Policyd v1
Policyd v1 is an anti-spam plugin for Postfix (written in C) that does Greylisting, Sender-(envelope, SASL or host / ip)-based throttling (on messages and/or volume per defined time unit), Recipient rate limiting, Spamtrap monitoring / blacklisting, HELO auto blacklisting and HELO randomization prevention. Policyd v1 is only open for bug & security fixes, everyone is strongly advised to migrate to v2.