Open-source transactional email
We track 5 open-source email platforms with a send API, each checked for licence, commercial use, hardware, paid services and setup. None has confirmed local running, commercial use and no required paid service together yet, so check each row. Easiest to set up: listmonk.
Facts checked 28 Oct 2026. Each project’s page shows the source and date for every answer.
Transactional email is the one-to-one mail your app sends when something happens, such as a receipt, a sign-up confirmation or a password reset. Each project below documents an API (or SMTP) for sending it, and most also do newsletters.
Self-hosting the software doesn't mean you deliver the mail yourself. Some send through a provider such as Amazon SES, which is billed per email; the paid-services column shows which.
Compared
| Compare | Project | Runs on my machine | Allowed at work | Paid services | Setup | Runs on | Stars |
|---|---|---|---|---|---|---|---|
| listmonkSelf-hosted newsletter and mailing list manager in a single Go binary with PostgreSQL; lists, SQL segments, templates, analytics and archives. | Yes | ConditionsAGPL-3.0 | Optional only | Easy | Windows, macOS, Linux | 24k | |
| PlunkOpen-source email platform for transactional mail, campaigns and workflow automations with segments and open/click analytics; sends via AWS SES. | Yes | ConditionsAGPL-3.0 | Required | Medium | Not confirmed | 5.6k | |
| useSendOpen-source sending platform on top of Amazon SES with transactional API, SMTP, contacts and marketing emails; formerly Unsend; still in beta. | Yes | ConditionsAGPL-3.0 | Required | Medium | Not confirmed | 4.8k | |
| NotifuseSelf-hosted newsletter and transactional email platform in Go; MJML builder, A/B tests, visual automations, analytics. Source-available (BSL) since v40. | Yes | ConditionsBusiness Source License 1.1, not OSI open source | Optional only | Medium | Not confirmed | 2.3k | |
| BillionMailSelf-hosted mail server plus email marketing from the aaPanel team; contacts, tags, templates, campaigns and open/click stats, sending from your own server. | Yes | ConditionsAGPL-3.0 | None required | Medium | Linux | 16k |
Tick up to three to compare them side by side. Ordered by our ranking (stars 40%, recent activity 30%, how many facts we could source 30%), so a well-documented, active project can sit above a bigger one. Unknown means we found no source, never a yes. Stars show attention, not quality. How we check and rank.
Where to start, by what matters to you
Each one comes from a sourced fact on the project’s page, not from a sponsor or a test score.
Common questions
Is there a free, self-hosted transactional email service?
Yes. BillionMail needs no paid service at all. listmonk and Notifuse are free to run, with paid services optional or depending on your setup. The software is free; what you may pay for is the server it runs on and any outside service it relies on, which the paid-services column lists.
Which run in Docker?
All 5 can run on your own server: listmonk, Plunk, useSend, Notifuse and BillionMail. All of them document a Docker setup. Setup is rated easy for listmonk.
Which can I use commercially?
With conditions: listmonk, Plunk, useSend, Notifuse and BillionMail. This is not legal advice; read each licence.
Which is easiest to set up?
Rated easy from their install docs: listmonk. Each page links the exact install step we checked.
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