12 Best Open-Source Email Tools (2026), Tested
A reference stack for teams that want to own every layer.
criteria
- License
- Operational maturity
- Community
- 01
Postal
Self-hosted TransactionalOutbound and inbound delivery server.
- 02
mailcow
Self-hostedFull self-hosted mail and groupware suite with a strong admin UI.
- 03
maddy
Self-hostedCompact all-in-one SMTP, MX, IMAP, and authentication stack.
- 04
Listmonk
Newsletter Self-hostedNewsletter manager and broadcast.
- 05
Novu
Notifications Self-hostedNotification orchestration across channels.
- 06
Cuttlefish
Self-hosted TransactionalTransactional email dashboard with SMTP, bounce handling, and analytics.
- 07
Mailpit
TestingLocal capture for dev and staging.
- 08
React Email
TemplatesTemplates as React components.
- 09
MJML
TemplatesVendor-neutral template language.
- 10
Foundation for Emails
TemplatesResponsive email framework with Inky, Sass, templates, and inlining.
- 11
Handlebars
TemplatesSimple MIT-licensed template layer used across many email renderers.
- 12
Liquid
TemplatesSafe user-editable template language with strong commerce adoption.
All 12 compared
Every provider in this ranking against the priorities growth and lifecycle teams weigh. Free tier and entry price sit with each pick above.
| Provider | Scheduling | Event stream | Operating since | Suppressions API | Best published rate per 1,000 | Multi-tenant |
|---|---|---|---|---|---|---|
| Postal | No | Yes | Not published | Yes | Tiers not published in comparable form | Yes |
| mailcow | No | Yes | Not published | Yes | Tiers not published in comparable form | Yes |
| maddy | No | No | Not published | No | Tiers not published in comparable form | Yes |
| Listmonk | Yes | Yes | Not published | Yes | Tiers not published in comparable form | No |
| Novu | Yes | Yes | 2021 | Yes | Tiers not published in comparable form | Yes |
| Cuttlefish | No | Yes | Not published | Yes | Tiers not published in comparable form | Yes |
| Mailpit | No | No | Not published | No | Tiers not published in comparable form | No |
| React Email | No | No | Not published | No | Tiers not published in comparable form | No |
| MJML | No | No | Not published | No | Tiers not published in comparable form | No |
| Foundation for Emails | No | No | Not published | No | Tiers not published in comparable form | No |
| Handlebars | No | No | Not published | No | Tiers not published in comparable form | No |
| Liquid | No | No | Not published | No | Tiers not published in comparable form | No |
If you are growth and lifecycle teams
Growth work lives or dies on targeting and measurement. What matters is whether behavioral triggers can be built without engineering time, whether the event stream supports attribution past the open, and whether deliverability holds when broadcast volume shares a reputation with product email.
The order above is the general editorial ranking. Re-sorted against scheduling, event stream, and operating track record, the shortlist for behavior-triggered journeys, broadcasts, and winback campaigns measured on revenue becomes Novu, Listmonk, and Postal. That differs from the headline order, which weighs all audiences together.