qmail fork with IPV6, TLS, DANE, DKIM, SRS2, SPF, daemontools, qmailanalog, mess822, & ucspi-tcp

The Mailismus mailserver - SMTP, IMAP, POP3, SSL

Web interface for SQLgrey built on Laravel 5

List of "big mailers" for OpenBSD's 'smtpctl spf walk' mechanism

gld, a lightweight greylist daemon for postfix

Greylisting of suspicious source (exported from code.google.com/p/gross)

Postfix policy application written in Go

dynamic and optionally distributed greylisting daemon

Foghorn is an extensibly DNS proxy and recursive resolver. The plugins are where the magic happens, replace pihole, add your /etc/hosts to your network dns, serve zone files, run as a dev server which returns fuzzed responses and other errors. UDP/TCP/DoT/DoH upstream and down. DNSSEC Support. Bend DNS to your will!

OpenSMTPd filter for quick and dirty greylisting

Verify email(s) using correct SMTP conversations (HELO / MAIL FROM /RCPT TO)

A tool to kep the Unifi Country Blocklist Updated

Haraka plugin that implements greylisting