dgrey is a greylisting policy server that allows greylist information to be synchronized between multiple mail servers. All information is shared between the nodes and the nodes are equal; there is no master. The nodes may lose communication for a while and still be able to correctly resynchronize later. This works because all nodes keep a log of changes to the database. All communication is done across TCP connections, which can optionally be password protected. dgrey works with mail transfer agents such as Postfix and Exim.
jSieve is a Java implementation of the Sieve mail filtering language defined by RFC 3028. Sieve is an extensible mail filtering language. Its limited expressiveness (no loops or variables and no tests with side effects) allows user created scripts to be run safely on email servers. Sieve is targeted at the final delivery phase (where an incoming email is transferred to a user's mailbox). jSieve is implemented as a language processor that can be plugged into any Internet mail application to add Sieve support.
python-managesieve is a ManageSieve client library for remotely managing Sieve scripts, including a user application (the interactive 'sieveshell'). Sieve scripts allow users to filter incoming email on the mail server. The ManageSieve protocol allows managing Sieve scripts on a remote mail server. These servers are commonly sealed so that users cannot log into them, yet users must be able to update their scripts on them.This module allows accessing a Sieve server for managing Sieve scripts. It is accompanied by a simple yet functional user application, 'sieveshell'.
GLD-fork is a fork of the GLD program by Salim Gasmi. The fork has been made because the original project has been dead for many years, and some new featured were needed. GLD-fork, as with the original GLD, adds greylisting functionality to the Postfix mail server. Greylisting is a fairly resource friendly anti-spam technique. GLD-fork can easily be combined with other (more resource consuming) tools to build anti-spam protection.