Mailpit is an email testing tool for developers. It acts as an SMTP server, captures all sent emails, and displays them in a modern web interface. It also provides a REST API for integration testing.

Key features: - Fast, lightweight, and low memory usage - Multi-platform support (Linux, macOS, Windows) - Modern web UI for viewing emails - REST API for automated testing - Support for SMTP relay - Message tagging and search - Real-time web UI updates