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MailHog vs smtp4dev: catalog facts
MailHog	smtp4dev
Free Free and open source under the MIT licence.	Free Free to download, with the source code published on GitHub.
Windows, macOS, Linux, Self-hosted, Command line	Web, Self-hosted
Single Go binary that runs without installation Web UI and API for inspecting captured mail	Captures outgoing email so test messages never reach real inboxes Web interface for inspecting captured messages
Little development activity; last commit in early 2024 Intended for testing, not for delivering production mail	Meant for development and testing, not for sending real mail Documentation lives mainly in the repository
Downloadable app, Self-hosted	Downloadable app, Self-hosted
Open source	Closed source
License: MIT	License not stated
No account needed	No account needed
Works offline	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.