devmail

               SMTP                POP3     
Your app(s) ----------> devmail ----------> Thunderbird/Mail.app/Outlook/...

SMTP and POP3 server with no storage. It keeps all the mails in memory until they are fetched or until you shut down the program. It is meant for developers who need to inspect the mail that their app sends. You can send emails to it via SMTP and "pop" them with an e-mail client like Thunderbird or Mail.app on macOS. It is comparable to Letter Opener.

This is a port of Blue Rail's Post Office to Crystal-lang.