Best Open Source Alternatives to Mailbird

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

Curated by open-source.store · Updated November 2026 · 4 alternatives

Mailbird

Proprietary SaaS

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Mailbird alternatives compared

Open-source alternatives to Mailbird, compared by stars, license and platform
Tool		License	Platforms	Self-hosted
Thunderbird	14,172	Apache-2.0	LinuxmacOSWindowsandroid	No	Nov 2026	Visit
Mailpile	8,806	AGPL-3.0	LinuxmacOSWindows	Yes	Nov 2023	Visit
Roundcube	7,256	GPL-3.0	LinuxmacOSWindowsDocker	Yes	Oct 2026	Visit
NeoMutt	3,859	GPL-2.0	LinuxmacOSWindows	No	Nov 2026	Visit

Top open-source Mailbird alternatives

Thunderbird14,172Apache-2.0

Thunderbird is an open-source email client replacing Microsoft Outlook with unified inboxes, native CalDAV calendar sync, and zero subscription costs.

LinuxmacOSWindowsandroidios

vs Mailbird: a free, open-source option you fully control, licensed Apache-2.0.

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Mailpile8,806AGPL-3.0

Mailpile is a self-hosted email client offering local search and OpenPGP encryption, replacing cloud webmail with private, user-managed mailboxes.

LinuxmacOSWindows

vs Mailbird: a free, open-source option you fully control, licensed AGPL-3.0.

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Roundcube7,256GPL-3.0

Roundcube provides self-hosted open-source webmail for IMAP servers, replacing costly Microsoft Outlook seats with clean browser-based message triage.

LinuxmacOSWindowsDockerWeb

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

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NeoMutt3,859GPL-2.0

NeoMutt is a command-line email client that replaces desktop apps like Microsoft Outlook with fast, scriptable terminal-based inbox management.

LinuxmacOSWindows

vs Mailbird: a free, open-source option you fully control, licensed GPL-2.0.

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Best Open Source Alternatives to Mailbird

Mailbird

Mailbird alternatives compared

Top open-source Mailbird alternatives

The modern standard for Protobuf workflows

Mentoring for backend developers. Consulting for startups.