Policy Daemon

The Policy Daemon project is a must-have anti-spam plugin for Postfix. It is written in C, ensuring optimal performance and efficiency. One of its most remarkable features is Greylisting. This technique prevents spammers from delivering their messages by initially delaying all incoming emails from unknown senders.

Policy Daemon also offers Sender-based throttling, giving you control over messages and/or volume per defined time unit. With this feature, you can define a limit on the number of messages that can be sent from a particular host or IP address, greatly reducing the chances of email overload.

Another powerful capability of Policy Daemon is recipient rate limiting. Through this feature, you can define the maximum number of messages that can be sent to a specific recipient within a certain time frame. This ensures that no single recipient is inundated with too many messages, preventing the server from getting overwhelmed.

Lastly, Policy Daemon provides spamtrap monitoring and blacklist functionality, guarding against unchecked spam messages. Any incoming spam can be automatically flagged, blacklisted, or sent to a spamtrap for further scrutiny.

Overall, the Policy Daemon project is an essential tool for anyone looking to improve their Postfix's spam-prevention capabilities. Its features and ease-of-use make it an excellent addition to any anti-spam toolkit.