* [Exim](http://www.exim.org/) - Message transfer agent (MTA) developed at the University of Cambridge.
* [Haraka](http://haraka.github.io/) - A high-performance, pluginable SMTP server written in JavaScript.
* [MailCatcher](http://mailcatcher.me/) - Ruby gem that deploys a simply SMTP MTA gateway that accepts all mail and displays in web interface. Useful for debugging or development.
@ -165,7 +166,6 @@ Some [Groupware](#groupware) solutions also feature calendar/address book editin
*MDA - Mail Delivery Agents (IMAP/POP3 software).*