milter manager is a free software to protect you from spam mails and virus mails effectively with milter.

Pure Python-asyncio Milter framework

It's a lightweight, fast and reliable Sendmail milter that implements the Sender Policy Framework

Correct configuration for mail server on Ubuntu with spf and dkim authentication

Milter interface for the amavis spam filter engine.

OpenPGP milter service to automatically PGP encrypt plaintext emails when possible

Postfix statistics implemented as a milter written in Go

signing-milter enables you to s/mime sign an ordinary mail while passing a MTA. Base on https://signing-milter.org/ by Andreas Schulze

Scripts to prevent a mail server from generating backscatter

Exchange Online Tenant Authorisation Milter (Mail-Filter)

SPEC files and Patches for OpenDKIM Fedora / EPEL RPMs

Golang Milter Client

A milter that performs DKIM and ARC signatures.

Parse incoming emails for statistics

pymilter-based daemon to safely classify email using dspam

Milter for filtering emails according MAIL FROM domain.

SPEC files and Patches for OpenDMARC Fedora / EPEL RPMs

The Mailmunge email filtering framework

Limit the number of messages by connecting client IP, sender, or recipient.

This is my workaround for zimbra's postfix issue for preventing authenticated user can modify FROM: in email address