dkim

Mailu/Mailu

+17

Insular email distribution - mail server as Docker images

foxcpp/maddy

+5

✉️ Composable all-in-one mail server.

retlehs/quien

+4

A better whois and domain intelligence toolkit

haraka/Haraka

+4

A fast, highly extensible, and event driven SMTP server

parsedmarc

+3

A Python package and CLI for parsing aggregate and forensic DMARC reports

awesome-opensource-email

+2

Awesome Opensource Email Resources

MailKit

+2

A cross-platform .NET library for IMAP, POP3, and SMTP.

MimeKit

+1

A .NET MIME creation and parser library with support for S/MIME, PGP, DKIM, TNEF and Unix mbox spools.

sentio

+1

Email inbox API for AI agents. Give every agent its own real email address, receive mail as structured webhooks, and reply in-thread over REST. A complete multi-tenant mail server in Rust: inbound and outbound, DKIM/SPF/DMARC/ARC, MTA-STS, DANE, three-tier anti-spam.