- [Cyrus IMAP/POP3](http://cyrusimap.org/) - Intended to be run on sealed servers, where normal users are not permitted to log in. ([Source Code](https://github.com/cyrusimap/cyrus-imapd )) `BSD-3-Clause-Attribution``C`
- [Cyrus IMAP/POP3](https://www.cyrusimap.org/) - Intended to be run on sealed servers, where normal users are not permitted to log in. ([Source Code](https://github.com/cyrusimap/cyrus-imapd )) `BSD-3-Clause-Attribution``C`
- [Dovecot](http://www.dovecot.org/) - IMAP and POP3 server written primarily with security in mind. ([Source Code](https://github.com/dovecot/core)) `MIT/LGPL-2.1``C`
- [Dovecot](http://www.dovecot.org/) - IMAP and POP3 server written primarily with security in mind. ([Source Code](https://github.com/dovecot/core)) `MIT/LGPL-2.1``C`