Self-hosted alternatives to Mailgun
Per-message pricing on top of a monthly floor, for a protocol that costs almost nothing to run.
Below are 10 open-source projects that cover the same ground, each scored 0–100 on how actively it is actually maintained — commit volume, release cadence and recent trend. 2 of the 10 are currently rated healthy or better. Ordering reflects that score, not sponsorship.
| Project | Health | Activity (11 mo) | Stars | Licence | Last release |
|---|---|---|---|---|---|
| Mailcow Mail server suite based on Dovecot, Postfix and other open source software, that provides a modern Web UI for | Healthy · 76 | 14k | GPL-3.0 | 21 Sept 2026 | |
| Mailu Simple yet full-featured mail server as a set of Docker images. | Healthy · 68 | 7.5k | MIT | 23 Sept 2026 | |
| Haraka Fast, highly extensible, and event driven SMTP server. | Steady · 57 | 5.6k | MIT | 5 Sept 2026 | |
| Postal Complete and fully featured mail server for use by websites & web servers. | Steady · 55 | 17k | MIT | 3 Jun 2026 | |
| OpenSMTPD Secure SMTP server implementation from the OpenBSD project. | At risk · 32 | 586 | ISC | 13 Sept 2026 | |
| DragonFly A small MTA for home and office use. Works on Linux and FreeBSD. | At risk · 20 | 265 | BSD-3-Clause | — | |
| chasquid SMTP (email) server with a focus on simplicity, security, and ease of operation. | Unrated | — | Apache-2.0 | — | |
| Courier MTA Fast, scalable, enterprise mail/groupware server providing ESMTP, IMAP, POP3, webmail, mailing list, basic web | Unrated | — | GPL-3.0 | — | |
| EmailRelay A small and easy to configure SMTP and POP3 server for Windows and Linux. | Unrated | — | GPL-3.0 | — | |
| Exim Message transfer agent (MTA) developed at the University of Cambridge. | Unrated | — | GPL-3.0 | — |
How these were picked
Every project listed here is open source and can run entirely on hardware you control. We start from the categories that match Mailgun's job — Communication - Email - Mail Transfer Agents — then rank by health score so that a popular-but-abandoned project never appears above a smaller one that is actively shipping. The scoring method is documented in full.
The scores are recomputed from repository data on every rebuild, so this page reflects the state of these projects as of 1 Oct 2026 — not the day it was written.
Mailcow
Mail server suite based on Dovecot, Postfix and other open source software, that provides a modern Web UI for administration.
Best fit: Self-hosters who need to run a full-featured mail server and prefer a unified web interface over manual configuration file editing.
Worth knowing: Running your own mail server involves significant operational burden regarding IP reputation, spam filtering, and DNS record management. Misconfiguration can easily lead to delivery failures.
Mailu
Simple yet full-featured mail server as a set of Docker images.
Best fit: It suits administrators who want to run their own email infrastructure using container orchestration tools rather than configuring raw postfix anddovecot packages by hand.
Worth knowing: Running a self-hosted mail server carries inherent operational burdens, particularly around IP reputation, spam filtering, and DNS record management like SPF and DKIM. Deliverability issues can be difficult to troubleshoot.
Haraka
Fast, highly extensible, and event driven SMTP server.
Best fit: It is suited for administrators looking to build custom email routing logic or security filters using JavaScript plugins rather than traditional configuration languages.
Worth knowing: Node-based mail servers demand careful monitoring of event loop blockages and memory limits under sustained high traffic loads, and they have a smaller community footprint than established alternatives like Postfix or Exim.
Postal
Complete and fully featured mail server for use by websites & web servers.
Best fit: It is a suitable choice if you need to run your own mail infrastructure to send and receive transactional emails from multiple web applications rather than relying on third-party SaaS providers.
Worth knowing: Running a self-hosted email server involves a high operational burden, particularly around maintaining domain reputation, handling DNS records like SPF, DKIM, and DMARC, and avoiding spam blacklists.
OpenSMTPD
Secure SMTP server implementation from the OpenBSD project.
Best fit: It is a suitable choice if you require a minimalist, security-focused mail transfer agent developed with OpenBSD's rigorous standards. It fits well into traditional Unix-like server setups.
Worth knowing: Configuration can be notoriously complex and documentation is often sparse compared to more mainstream alternatives like Postfix. Low development activity means you may need to rely heavily on community patches or internal expertise for troubleshooting.