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PostfixSimple NixOS Mailserver
Free

Free and open source.

 Free

Free and open source under the GPL-3.0 licence.

macOS, Linux, Self-hosted Linux, Self-hosted
  • Security-focused design
  • Runs on many Unix-like systems
  • Whole mail server defined declaratively in NixOS configuration
  • Releases track each NixOS release
  • Transfer agent only; needs a separate IMAP server for mailboxes
  • Configuration requires mail server knowledge
  • 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

Checked September 24, 2026

Checked October 2, 2026

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