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 August 2026 · 5 alternatives

Mailbird

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Mailbird alternatives compared

Open-source alternatives to Mailbird, compared by stars, license and platform
Tool		License	Platforms	Self-hosted
Thunderbird	13,775	GPL-3.0	LinuxmacOSWindowsandroid	No	Jul 2026	Visit
K-9 Mail	13,774	Apache-2.0	android	No	Jul 2026	Visit
Mailpile	8,829	AGPL-3.0	LinuxmacOSWindows	Yes	Nov 2023	Visit
Roundcube	7,106	GPL-3.0	LinuxmacOSWindowsDocker	Yes	Jul 2026	Visit
NeoMutt	3,796	GPL-2.0	LinuxmacOSWindows	No	Jul 2026	Visit