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OpenSMTPDPostal
Free

Free and open source under the ISC license.

 Free

Free and open source to run on your own server.

Linux, Self-hosted, Command line Self-hosted
  • Part of the OpenBSD project
  • Simpler than many other SMTP servers
  • Self-hosted alternative to hosted transactional email services
  • Handles both sending and receiving mail
  • A mail server, not a client for reading email
  • Needs other components for a complete mail setup
  • Requires running and maintaining your own mail server
  • Deliverability depends on your own server reputation and setup
Downloadable app, Self-hosted Self-hosted
Open source Open source
License: ISC License not stated
No account needed No account 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.