# Best open source email servers > The best open source email server is Stalwart Mail Server, with 14,971 GitHub stars, the AGPL-3.0 license and a Docker image; Mailcow and docker-mailserver are strong alternatives. 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. The overall ranking weighs GitHub stars, commits in the last year, Docker images, open-source licenses and recent commits across the 24 apps in the email servers category of the appsgit catalog. ## Key facts | Fact | Value | |---|---| | Question | What is the best open source email server? | | Picks | 25 | | Top pick | Stalwart Mail Server (14,971 stars) | | Data as of | Oct 7, 2026 | | Canonical URL | https://appsgit.com/best/open-source-email-servers | ## Top picks 10 of the 24 apps in the email servers category, ranked on GitHub stars, commits in the last year, Docker images, open-source licenses and recent commits. - [Stalwart Mail Server](https://appsgit.com/apps/stalwart-mail-server) (14,971 stars, AGPL-3.0, Rust, Docker): Stalwart Mail Server has 14,971 GitHub stars, uses the AGPL-3.0 license, ships a Docker image and had 679 commits in the last year; it replaces Twilio SendGrid and Mailgun. - [Mailcow](https://appsgit.com/apps/mailcow) (13,563 stars, GPL-3.0, JavaScript, Docker): Mailcow has 13,563 GitHub stars, uses the GPL-3.0 license, ships a Docker image and had 316 commits in the last year; it replaces Google Workspace and Microsoft 365. - [docker-mailserver](https://appsgit.com/apps/docker-mailserver) (18,903 stars, MIT, Shell, Docker): docker-mailserver has 18,903 GitHub stars, uses the MIT license, ships a Docker image and had 107 commits in the last year; it replaces Gmail. - [Postal](https://appsgit.com/apps/postal) (16,854 stars, MIT, Ruby, Docker): Postal has 16,854 GitHub stars, uses the MIT license, ships a Docker image and had 18 commits in the last year; it replaces Twilio SendGrid and Mailgun. - [SimpleLogin](https://appsgit.com/apps/simplelogin) (7,037 stars, AGPL-3.0, Python, Docker): SimpleLogin has 7,037 GitHub stars, uses the AGPL-3.0 license, ships a Docker image and had 250 commits in the last year. - [Mailu](https://appsgit.com/apps/mailu) (7,537 stars, MIT, Python, Docker): Mailu has 7,537 GitHub stars, uses the MIT license, ships a Docker image and had 169 commits in the last year; it replaces Gmail. - [Roundcube](https://appsgit.com/apps/roundcube) (7,207 stars, GPL-3.0, PHP): Roundcube has 7,207 GitHub stars, uses the GPL-3.0 license and had 260 commits in the last year; it replaces Gmail. - [Mail-in-a-Box](https://appsgit.com/apps/mail-in-a-box) (15,435 stars, CC0-1.0, Python): Mail-in-a-Box has 15,435 GitHub stars, uses the CC0-1.0 license and had 20 commits in the last year; it replaces Gmail. - [AnonAddy](https://appsgit.com/apps/anonaddy) (4,885 stars, AGPL-3.0, PHP, Docker): AnonAddy has 4,885 GitHub stars, uses the AGPL-3.0 license, ships a Docker image and had 67 commits in the last year. - [Modoboa](https://appsgit.com/apps/modoboa) (3,542 stars, ISC, Python): Modoboa has 3,542 GitHub stars, uses the ISC license and had 765 commits in the last year. ## Best for startups Ranked for startups on GitHub stars, commits in the last year, Docker images, open-source licenses, project websites and recent commits. - [docker-mailserver](https://appsgit.com/apps/docker-mailserver) (18,903 stars, MIT, Shell, Docker): docker-mailserver has 18,903 GitHub stars, uses the MIT license, ships a Docker image and had 107 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. - [Stalwart Mail Server](https://appsgit.com/apps/stalwart-mail-server) (14,971 stars, AGPL-3.0, Rust, Docker): Stalwart Mail Server has 14,971 GitHub stars, uses the AGPL-3.0 license, ships a Docker image and had 679 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. - [Mailcow](https://appsgit.com/apps/mailcow) (13,563 stars, GPL-3.0, JavaScript, Docker): Mailcow has 13,563 GitHub stars, uses the GPL-3.0 license, ships a Docker image and had 316 commits in the last year; it replaces Google Workspace and Microsoft 365. For startups it also scores on a Docker image, an open-source license, a project website and a commit in the last 90 days. - [Postal](https://appsgit.com/apps/postal) (16,854 stars, MIT, Ruby, Docker): Postal has 16,854 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. - [Mailu](https://appsgit.com/apps/mailu) (7,537 stars, MIT, Python, Docker): Mailu has 7,537 GitHub stars, uses the MIT license, ships a Docker image and had 169 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. ## Best for small business Ranked for small business on GitHub stars, commits in the last year, Docker images, open-source licenses, project websites, recent commits and deploy guides. - [Stalwart Mail Server](https://appsgit.com/apps/stalwart-mail-server) (14,971 stars, AGPL-3.0, Rust, Docker): Stalwart Mail Server has 14,971 GitHub stars, uses the AGPL-3.0 license, ships a Docker image and had 679 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. - [Mailcow](https://appsgit.com/apps/mailcow) (13,563 stars, GPL-3.0, JavaScript, Docker): Mailcow has 13,563 GitHub stars, uses the GPL-3.0 license, ships a Docker image and had 316 commits in the last year; it replaces Google Workspace and Microsoft 365. 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. - [docker-mailserver](https://appsgit.com/apps/docker-mailserver) (18,903 stars, MIT, Shell, Docker): docker-mailserver has 18,903 GitHub stars, uses the MIT license, ships a Docker image and had 107 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. - [Postal](https://appsgit.com/apps/postal) (16,854 stars, MIT, Ruby, Docker): Postal has 16,854 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 small business it also scores on a Docker image, an open-source license, a project website and a commit in the last 90 days. - [SimpleLogin](https://appsgit.com/apps/simplelogin) (7,037 stars, AGPL-3.0, Python, Docker): SimpleLogin has 7,037 GitHub stars, uses the AGPL-3.0 license, ships a Docker image and had 250 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. ## Best for enterprise Ranked for enterprise on GitHub stars, commits in the last year, open-source licenses and recent commits. - [Stalwart Mail Server](https://appsgit.com/apps/stalwart-mail-server) (14,971 stars, AGPL-3.0, Rust, Docker): Stalwart Mail Server has 14,971 GitHub stars, uses the AGPL-3.0 license, ships a Docker image and had 679 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. - [docker-mailserver](https://appsgit.com/apps/docker-mailserver) (18,903 stars, MIT, Shell, Docker): docker-mailserver has 18,903 GitHub stars, uses the MIT license, ships a Docker image and had 107 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. - [Mailcow](https://appsgit.com/apps/mailcow) (13,563 stars, GPL-3.0, JavaScript, Docker): Mailcow has 13,563 GitHub stars, uses the GPL-3.0 license, ships a Docker image and had 316 commits in the last year; it replaces Google Workspace and Microsoft 365. For enterprise it also scores on an open-source license and a commit in the last 90 days. - [Postal](https://appsgit.com/apps/postal) (16,854 stars, MIT, Ruby, Docker): Postal has 16,854 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. - [Mail-in-a-Box](https://appsgit.com/apps/mail-in-a-box) (15,435 stars, CC0-1.0, Python): Mail-in-a-Box has 15,435 GitHub stars, uses the CC0-1.0 license and had 20 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. ## How this list was made - Candidates: the 24 apps in the email servers category. Archived projects and projects with no commit in the last two years are left out. - Base score: GitHub stars on a log scale plus commits in the last 12 months (log scale, capped at 1,000). - Bonus points for a published Docker image, an OSI-approved open-source license and a commit in the last 90 days. - Each "Best for" section re-ranks the same apps with that audience's profile (for example startups add points for permissive licenses, project websites and recent commits; small business for Docker images and deploy guides). - Source-available apps can rank, but they are labelled and never described as open source. ## FAQ ### 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. ### Which open source email server is best for a startup? docker-mailserver ranks first for startups, with 18,903 GitHub stars, the MIT license and a Docker image; Stalwart Mail Server and Mailcow follow. The startups ranking adds points for Docker images, permissive licenses, project websites and recent commits on top of stars and activity. ### Which open source email server is best for a small business? Stalwart Mail Server ranks first for small business, with 14,971 GitHub stars, the AGPL-3.0 license and a Docker image; Mailcow and docker-mailserver follow. The small business ranking adds points for Docker images, open-source licenses, project websites, recent commits and deploy guides on top of stars and activity. ### Can I self-host these email servers with Docker? Yes, 7 of the 10 picks. Stalwart Mail Server, Mailcow and docker-mailserver 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. ## Related questions - [What is the best open source budgeting app?](https://appsgit.com/best/open-source-budgeting-software) - [What is the best open source CMS?](https://appsgit.com/best/open-source-cms) - [What is the best open source team chat app?](https://appsgit.com/best/open-source-team-chat) - [What is the best open source file sharing app?](https://appsgit.com/best/open-source-file-sharing) - [What is the best open source analytics tool?](https://appsgit.com/best/open-source-analytics) - [What is the best open source developer tool?](https://appsgit.com/best/open-source-developer-tools) - [What is the best open source file sync and storage app?](https://appsgit.com/best/open-source-file-sync) - [What is the best open source database tool?](https://appsgit.com/best/open-source-database-tools) ## See also - [All email servers apps](https://appsgit.com/categories/email-servers) - [All groupware & calendars apps](https://appsgit.com/categories/groupware-calendars) - [All utilities apps](https://appsgit.com/categories/utilities) - [Open-source alternatives to Twilio SendGrid](https://appsgit.com/alternatives/sendgrid) - [Open-source alternatives to Mailgun](https://appsgit.com/alternatives/mailgun) - [Open-source alternatives to Gmail](https://appsgit.com/alternatives/gmail) - [Open-source alternatives to Google Workspace](https://appsgit.com/alternatives/google-workspace) - [Open-source alternatives to Microsoft 365](https://appsgit.com/alternatives/microsoft-365) --- Canonical page: https://appsgit.com/best/open-source-email-servers Source: appsgit (https://appsgit.com), the app store for github. Data from the GitHub API, refreshed nightly. Machine access: JSON API https://appsgit.com/api/v1/apps (OpenAPI: https://appsgit.com/openapi.json), MCP server https://mcp.appsgit.com/mcp, full index https://appsgit.com/llms-full.txt.