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smtp4devPapercut SMTP
Free

Free to download, with the source code published on GitHub.

 Free

Free and open source under the Apache-2.0 licence.

Web, Self-hosted Windows, Self-hosted
  • Captures outgoing email so test messages never reach real inboxes
  • Web interface for inspecting captured messages
  • Catches test emails without sending them
  • Simple desktop interface for reading captured messages
  • Meant for development and testing, not for sending real mail
  • Documentation lives mainly in the repository
  • Meant for testing, not a real mail server
  • Desktop app is Windows-only
Downloadable app, Self-hosted Downloadable app, Self-hosted
Closed source Open source
License not stated License: Apache-2.0
No account needed No account needed
Works offline Works offline

Checked October 2, 2026

Checked October 2, 2026

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