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10 top picks · 3 audience rankings

Best open source email servers

The best open source email server is Stalwart Mail Server (AGPL-3.0, 15,442 GitHub stars, Docker image). docker-mailserver stands out for the most GitHub stars, and Mailcow stands out for its JavaScript codebase.

This page also breaks the picks down by team size and use: docker-mailserver leads for startups; Stalwart Mail Server for small business and enterprise.

Updated · data from GitHub, refreshed daily

Top picks

  1. Rank 1:

    Stalwart Mail Server

    stalwartlabs/stalwart

    All-in-one mail server with JMAP, IMAP4, and SMTP support and a wide range of modern features.

    Active · last commit Oct 27, 2026

    Email ServersRustDocker

    Stands out for the most commits in the last 12 months (714). Stalwart Mail Server has 15,442 GitHub stars, uses the AGPL-3.0 license, ships a Docker image and had 714 commits in the last year; it replaces Twilio SendGrid and Mailgun.

  2. Rank 2:

    docker-mailserver

    docker-mailserver/docker-mailserver

    Production-ready fullstack but simple mail server (SMTP, IMAP, LDAP, Antispam, Antivirus, etc.) running inside a container. Only configuration files, no SQL database.

    Active · last commit Oct 26, 2026

    Email ServersShellDocker

    Stands out for the most GitHub stars. docker-mailserver has 19,698 GitHub stars, uses the MIT license, ships a Docker image and had 119 commits in the last year; it replaces Gmail.

  3. Rank 3:

    Mailcow

    mailcow/mailcow-dockerized

    Mail server suite based on Dovecot, Postfix and other open source software, that provides a modern Web UI for administration.

    Active · last commit Oct 28, 2026

    Email ServersJavaScriptDocker

    Stands out for its JavaScript codebase. Mailcow has 13,712 GitHub stars, uses the GPL-3.0 license, ships a Docker image and had 353 commits in the last year; it replaces Gmail.

At a glance

Open source email servers compared

Ranked on GitHub stars, commits in the last year, Docker images, open-source licenses and recent commits across the 24 apps in the email servers category. Projects with fewer than 12 commits in the last 12 months rank below every more active project.

Top 10 picks compared, data as of Oct 28, 2026
AppStands out forLicenseGitHub starsCommits (12 mo)Last commitDocker image
Stalwart Mail Serverthe most commits in the last 12 months (714)AGPL-3.015,442714Oct 27, 2026Yes
docker-mailserverthe most GitHub starsMIT19,698119Oct 26, 2026Yes
Mailcowits JavaScript codebaseGPL-3.013,712353Oct 28, 2026Yes
Mailua permissive MIT licenseMIT7,595279Oct 27, 2026Yes
SimpleLogin–AGPL-3.07,097307Oct 27, 2026Yes
Postal–MIT16,89718Oct 20, 2026Yes
Roundcube–GPL-3.07,245308Oct 25, 2026No
Mail-in-a-Box–CC0-1.015,45023Oct 22, 2026No
AnonAddy–AGPL-3.04,92469Oct 6, 2026Yes
Modoboa–ISC3,545910Oct 28, 2026No

1 of 4 · 10 picks

Top picks

10 of the 24 apps in the email servers category.

  1. 1

    Stalwart Mail Server

    All-in-one mail server with JMAP, IMAP4, and SMTP support and a wide range of modern features.

    Stands out for the most commits in the last 12 months (714). Stalwart Mail Server has 15,442 GitHub stars, uses the AGPL-3.0 license, ships a Docker image and had 714 commits in the last year; it replaces Twilio SendGrid and Mailgun.

  2. 2

    docker-mailserver

    Production-ready fullstack but simple mail server (SMTP, IMAP, LDAP, Antispam, Antivirus, etc.) running inside a container. Only configuration files, no SQL database.

    Stands out for the most GitHub stars. docker-mailserver has 19,698 GitHub stars, uses the MIT license, ships a Docker image and had 119 commits in the last year; it replaces Gmail.

  3. 3

    Mailcow

    Mail server suite based on Dovecot, Postfix and other open source software, that provides a modern Web UI for administration.

    Stands out for its JavaScript codebase. Mailcow has 13,712 GitHub stars, uses the GPL-3.0 license, ships a Docker image and had 353 commits in the last year; it replaces Gmail.

  4. 4

    Mailu

    Simple yet full-featured mail server as a set of Docker images.

    Stands out for a permissive MIT license. Mailu has 7,595 GitHub stars, uses the MIT license, ships a Docker image and had 279 commits in the last year; it replaces Gmail.

  5. 5

    SimpleLogin

    Open source email alias solution to protect your email address. Comes with browser extensions and mobile apps.

    SimpleLogin has 7,097 GitHub stars, uses the AGPL-3.0 license, ships a Docker image and had 307 commits in the last year.

  6. 6

    Postal

    Complete and fully featured mail server for use by websites & web servers.

    Postal has 16,897 GitHub stars, uses the MIT license, ships a Docker image and had 18 commits in the last year; it replaces Twilio SendGrid and Mailgun.

  7. 7

    Roundcube

    Browser-based IMAP client with an application-like user interface.

    Roundcube has 7,245 GitHub stars, uses the GPL-3.0 license and had 308 commits in the last year; it replaces Gmail.

  8. 8

    Mail-in-a-Box

    Turns any Ubuntu server into a fully functional mail server with one command.

    Mail-in-a-Box has 15,450 GitHub stars, uses the CC0-1.0 license and had 23 commits in the last year; it replaces Gmail.

  9. 9

    AnonAddy

    Email forwarding service for creating aliases.

    AnonAddy has 4,924 GitHub stars, uses the AGPL-3.0 license, ships a Docker image and had 69 commits in the last year.

  10. 10

    Modoboa

    Mail hosting and management platform including a modern and simplified web user interface.

    Modoboa has 3,545 GitHub stars, uses the ISC license and had 910 commits in the last year.

2 of 4 · 5 picks

Which open source email server is best for startups?

For startups, docker-mailserver ranks first (MIT, 19,698 GitHub stars), followed by Stalwart Mail Server and Mailcow. Ranked for startups on GitHub stars, commits in the last year, Docker images, open-source licenses, project websites and recent commits.

  1. 1

    docker-mailserver

    Production-ready fullstack but simple mail server (SMTP, IMAP, LDAP, Antispam, Antivirus, etc.) running inside a container. Only configuration files, no SQL database.

    docker-mailserver has 19,698 GitHub stars, uses the MIT license, ships a Docker image and had 119 commits in the last year; it replaces Gmail. For startups it also scores on a Docker image, a permissive license (MIT), a project website and a commit in the last 90 days.

  2. 2

    Stalwart Mail Server

    All-in-one mail server with JMAP, IMAP4, and SMTP support and a wide range of modern features.

    Stalwart Mail Server has 15,442 GitHub stars, uses the AGPL-3.0 license, ships a Docker image and had 714 commits in the last year; it replaces Twilio SendGrid and Mailgun. For startups it also scores on a Docker image, an open-source license, a project website and a commit in the last 90 days.

  3. 3

    Mailcow

    Mail server suite based on Dovecot, Postfix and other open source software, that provides a modern Web UI for administration.

    Mailcow has 13,712 GitHub stars, uses the GPL-3.0 license, ships a Docker image and had 353 commits in the last year; it replaces Gmail. For startups it also scores on a Docker image, an open-source license, a project website and a commit in the last 90 days.

  4. 4

    Mailu

    Simple yet full-featured mail server as a set of Docker images.

    Mailu has 7,595 GitHub stars, uses the MIT license, ships a Docker image and had 279 commits in the last year; it replaces Gmail. For startups it also scores on a Docker image, a permissive license (MIT), a project website and a commit in the last 90 days.

  5. 5

    Postal

    Complete and fully featured mail server for use by websites & web servers.

    Postal has 16,897 GitHub stars, uses the MIT license, ships a Docker image and had 18 commits in the last year; it replaces Twilio SendGrid and Mailgun. For startups it also scores on a Docker image, a permissive license (MIT), a project website and a commit in the last 90 days.

3 of 4 · 5 picks

Which open source email server is best for small business?

For small business, Stalwart Mail Server ranks first (AGPL-3.0, 15,442 GitHub stars), followed by docker-mailserver and Mailcow. Ranked for small business on GitHub stars, commits in the last year, Docker images, open-source licenses, project websites, recent commits and deploy guides.

  1. 1

    Stalwart Mail Server

    All-in-one mail server with JMAP, IMAP4, and SMTP support and a wide range of modern features.

    Stalwart Mail Server has 15,442 GitHub stars, uses the AGPL-3.0 license, ships a Docker image and had 714 commits in the last year; it replaces Twilio SendGrid and Mailgun. For small business it also scores on a Docker image, an open-source license, a project website and a commit in the last 90 days.

  2. 2

    docker-mailserver

    Production-ready fullstack but simple mail server (SMTP, IMAP, LDAP, Antispam, Antivirus, etc.) running inside a container. Only configuration files, no SQL database.

    docker-mailserver has 19,698 GitHub stars, uses the MIT license, ships a Docker image and had 119 commits in the last year; it replaces Gmail. For small business it also scores on a Docker image, an open-source license, a project website and a commit in the last 90 days.

  3. 3

    Mailcow

    Mail server suite based on Dovecot, Postfix and other open source software, that provides a modern Web UI for administration.

    Mailcow has 13,712 GitHub stars, uses the GPL-3.0 license, ships a Docker image and had 353 commits in the last year; it replaces Gmail. For small business it also scores on a Docker image, an open-source license, a project website and a commit in the last 90 days.

  4. 4

    Mailu

    Simple yet full-featured mail server as a set of Docker images.

    Mailu has 7,595 GitHub stars, uses the MIT license, ships a Docker image and had 279 commits in the last year; it replaces Gmail. For small business it also scores on a Docker image, an open-source license, a project website and a commit in the last 90 days.

  5. 5

    SimpleLogin

    Open source email alias solution to protect your email address. Comes with browser extensions and mobile apps.

    SimpleLogin has 7,097 GitHub stars, uses the AGPL-3.0 license, ships a Docker image and had 307 commits in the last year. For small business it also scores on a Docker image, an open-source license, a project website and a commit in the last 90 days.

4 of 4 · 5 picks

Which open source email server is best for enterprise?

For enterprise, Stalwart Mail Server ranks first (AGPL-3.0, 15,442 GitHub stars), followed by docker-mailserver and Mailcow. Ranked for enterprise on GitHub stars, commits in the last year, open-source licenses and recent commits.

  1. 1

    Stalwart Mail Server

    All-in-one mail server with JMAP, IMAP4, and SMTP support and a wide range of modern features.

    Stalwart Mail Server has 15,442 GitHub stars, uses the AGPL-3.0 license, ships a Docker image and had 714 commits in the last year; it replaces Twilio SendGrid and Mailgun. For enterprise it also scores on an open-source license and a commit in the last 90 days.

  2. 2

    docker-mailserver

    Production-ready fullstack but simple mail server (SMTP, IMAP, LDAP, Antispam, Antivirus, etc.) running inside a container. Only configuration files, no SQL database.

    docker-mailserver has 19,698 GitHub stars, uses the MIT license, ships a Docker image and had 119 commits in the last year; it replaces Gmail. For enterprise it also scores on an open-source license and a commit in the last 90 days.

  3. 3

    Mailcow

    Mail server suite based on Dovecot, Postfix and other open source software, that provides a modern Web UI for administration.

    Mailcow has 13,712 GitHub stars, uses the GPL-3.0 license, ships a Docker image and had 353 commits in the last year; it replaces Gmail. For enterprise it also scores on an open-source license and a commit in the last 90 days.

  4. 4

    Postal

    Complete and fully featured mail server for use by websites & web servers.

    Postal has 16,897 GitHub stars, uses the MIT license, ships a Docker image and had 18 commits in the last year; it replaces Twilio SendGrid and Mailgun. For enterprise it also scores on an open-source license and a commit in the last 90 days.

  5. 5

    Mail-in-a-Box

    Turns any Ubuntu server into a fully functional mail server with one command.

    Mail-in-a-Box has 15,450 GitHub stars, uses the CC0-1.0 license and had 23 commits in the last year; it replaces Gmail. For enterprise it also scores on an open-source license and a commit in the last 90 days.

FAQ

Questions and answers

Still curious? Email info@appsgit.com.

Is Stalwart Mail Server free?

Yes. Stalwart Mail Server is open-source software released under the AGPL-3.0 license, so you can self-host it at no cost. You only pay for the server it runs on, and some projects also offer an optional paid cloud plan.

Can I self-host these email servers with Docker?

Yes, 7 of the 10 picks. Stalwart Mail Server, docker-mailserver and Mailcow publish Docker images, so you can run them on a VPS or home server with Docker Compose. The others install from their own packages or source; follow each project's install guide.

Are all of these email servers open source?

All 10 apps on this list are open source. You can self-host and modify each one under its license.

Which of these email servers is the most actively developed?

Modoboa, with 910 commits in the last 12 months and a latest release, 2.12.0, from October 2026. Activity is a good sign that bugs and security issues get fixed.

How is this list ranked?

Ranked on GitHub stars, commits in the last year, Docker images, open-source licenses and recent commits across the 24 apps in the email servers category. Projects with fewer than 12 commits in the last 12 months rank below every more active project.

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