Best Open Source Alternatives to StartMail

Compare the best free and open-source alternatives to StartMail — self-hosted and desktop replacements you fully control, ranked by GitHub stars, license and platform support.

Curated by open-source.store · Updated November 2026 · 2 alternatives

StartMail

Proprietary SaaS

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Platformsweb

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StartMail alternatives compared

Open-source alternatives to StartMail, compared by stars, license and platform
Tool		License	Platforms	Self-hosted
Mail-in-a-Box	15,454	CC0-1.0	Linux	Yes	Oct 2026	Visit
Mailcow	13,735	GPL-3.0	LinuxDocker	Yes	Nov 2026	Visit

Top open-source StartMail alternatives

Mail-in-a-Box15,454CC0-1.0

Mail-in-a-Box replaces Fastmail with an automated self-hosted email server featuring built-in DNSSEC, Nextcloud DAV sync, and Let's Encrypt TLS.

Linux

vs StartMail: a free, open-source option you fully control, licensed CC0-1.0.

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Mailcow13,735GPL-3.0

Mailcow replaces hosted email like Fastmail with a self-hosted Docker suite featuring Postfix, Dovecot, SOGo webmail, and automated TLS management.

LinuxDocker

vs StartMail: a free, open-source option you fully control, licensed GPL-3.0.

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Best Open Source Alternatives to StartMail

StartMail

StartMail alternatives compared

Top open-source StartMail alternatives

The modern standard for Protobuf workflows

Mentoring for backend developers. Consulting for startups.