smtp4dev

smtp4dev acts as a local dummy SMTP server for developers on Windows, Linux, or Mac OS-X, capturing outgoing emails to avoid spamming real users. It enables message retrieval via IMAP/POP3, logs SMTP sessions, and supports UTF8. Features include a mobile viewport switcher, multipart MIME inspector, and HTML compatibility checks. The server handles TLS/SSL with self-signed certs, authentication, and multiple mailboxes with rules for message routing. You can reply, compose, or relay messages automatically, and use scripting expressions to test scenarios like errors, all through an intuitive OpenAPI/Swagger interface.