smtp4dev

With smtp4dev, developers can test email functionalities without the risk of sending messages to live customers. This dummy SMTP server supports .NET Core on various OSes and includes IMAP/POP3 access to retrieve and delete trapped emails. It logs SMTP sessions, validates HTML, and inspects multipart MIME content. Advanced options include TLS/SSL encryption, authentication, and rule-based mailboxes for organizing messages. The tool allows relaying, composing, and auto-replying to emails, plus scripting for custom behaviors like error simulation, all accessible via OpenAPI for seamless integration into development pipelines.