# Open-source transactional email

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.

> 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 2026-10-28.

Give this to your agent: "Help me with this: "Open-source transactional email", using the RepoQuarry guide at https://repoquarry.dev/guides/open-source-transactional-email.md. Read the whole guide first, including its builds and links. Recommend the option that fits what I am building and why, check each project's official docs (linked there) before installing anything, ask me before spending money or using my accounts, and tell me what you set up when you finish."

## Best for…
- **Easiest to start:** [listmonk](https://repoquarry.dev/projects/listmonk.md). Setup rated easy: Easy; download binary or docker compose up, plus a PostgreSQL database
- **Nothing to pay for:** [BillionMail](https://repoquarry.dev/projects/billionmail.md). No paid service required: None required; built-in mail server sends directly if outbound port 25 is open, SMTP relay optional
- **Windows:** [listmonk](https://repoquarry.dev/projects/listmonk.md). Documented to run on Windows, macOS, Linux
- **Most popular:** [listmonk](https://repoquarry.dev/projects/listmonk.md). 24,279 GitHub stars, the most in this list

## Compared
Ordered by our ranking: stars 40%, recent activity 30%, sourced facts 30%.

| Project | Runs locally | Commercial use | Paid services | Setup | Platforms |
|---|---|---|---|---|---|
| [listmonk](https://repoquarry.dev/projects/listmonk.md) | Yes | Conditions · AGPL-3.0-only | Optional only | Easy | Windows, macOS, Linux |
| [Plunk](https://repoquarry.dev/projects/plunk.md) | Yes | Conditions · AGPL-3.0-only | Required | Medium | Not confirmed |
| [useSend](https://repoquarry.dev/projects/usesend.md) | Yes | Conditions · AGPL-3.0-only | Required | Medium | Not confirmed |
| [Notifuse](https://repoquarry.dev/projects/notifuse.md) | Yes | Conditions · BUSL-1.1 | Optional only | Medium | Not confirmed |
| [BillionMail](https://repoquarry.dev/projects/billionmail.md) | Yes | Conditions · AGPL-3.0-only | None required | Medium | Linux |

## 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.

## By paid product
- [Open-source alternatives to Brevo](https://repoquarry.dev/alternatives/brevo.md)
- [Open-source alternatives to Mailchimp](https://repoquarry.dev/alternatives/mailchimp.md)
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Source: RepoQuarry (https://repoquarry.dev/guides/open-source-transactional-email). Data licence: CC BY 4.0. Quotes are from project documentation and belong to their authors.