Open source smtp projects
Every project in the registry tagged smtp, ranked by real GitHub adoption.
Self-hosted newsletter and mailing list manager
Open-source mail server with unlimited sending & AI tools
BillionMail gives you open-source MailServer, NewsLetter, Email Marketing — fully self-hosted, dev-friendly, and free from monthly fees. Join the discord: http
Decentralized private messenger with chat-shared tools and games for Desktop
Open-source email API with enterprise deliverability
DavMail POP/IMAP/SMTP/CalDAV/CardDAV/LDAP Exchange and Office 365 Gateway - Synced with main subversion repository at
Official master for the Greenmail project
Related tags
Frequently asked questions
How many open source smtp projects are there?
This registry tracks 7 projects tagged smtp, with 58,706 GitHub stars between them. The most-adopted is Listmonk at 23,471 stars.
Are these smtp projects free to use?
Yes — 7 of the 7 carry an explicit open-source licence across 4 distinct licences, so there is no licence fee. Where a project also sells a hosted or enterprise version, the self-hosted path remains free.
Which smtp project should I choose?
The list above is ranked by GitHub stars, but stars measure attention rather than fit. Check three things on each card: the licence (permissive versus copyleft), the language it is written in, and the last-push date — a high-star project that has not been pushed in a year is a liability.
Are these smtp projects still maintained?
5 of the 7 were pushed in the last 90 days, and every card shows its exact last-push date so you can see the rest. Sort your shortlist by that date before committing to a migration.