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Papercut SMTP vs HELO: catalog facts
Papercut SMTP	HELO
Free Free and open source under the Apache-2.0 licence.	Paid Sold as a paid desktop application.
Windows, Self-hosted	macOS
Catches test emails without sending them Simple desktop interface for reading captured messages	Local SMTP server that catches mail before it reaches real users Automatic broken link check
Meant for testing, not a real mail server Desktop app is Windows-only	Paid only Laravel Herd Pro now includes its own email testing tool, which overlaps for PHP users
Downloadable app, Self-hosted	Downloadable app
Open source	Closed source
License: Apache-2.0	License not stated
No account needed	Not stated if an account is needed
Works offline	Not stated if it works offline
Official website Full listing and sources Checked October 2, 2026	Official website Full listing and sources Checked October 2, 2026

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