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Mailu vs Simple NixOS Mailserver: catalog facts
Mailu	Simple NixOS Mailserver
Free Free and open source.	Free Free and open source under the GPL-3.0 licence.
Linux, Self-hosted	Linux, Self-hosted
Webmail and admin interface included Per-domain delegation and quotas	Whole mail server defined declaratively in NixOS configuration Releases track each NixOS release
Requires Docker Releases are infrequent	Only works on NixOS Running a mail server still requires DNS and deliverability knowledge
Self-hosted	Self-hosted
Open source	Open source
License not stated	License: GPL-3.0
No account needed	Not stated if an account is needed
Not stated if it works offline	Not stated if it works offline
Official website Full listing and sources Checked September 24, 2026	Official website Full listing and sources Checked October 2, 2026

Catalog facts only. Anything “not stated” is unconfirmed. Check full listings for details.