* [EGroupware](http://www.egroupware.org/start.html) - Groupware software written in PHP.
* [Horde Groupware](http://www.horde.org/apps/groupware) - PHP based collaborative software suite that includes email, calendars, wikis, time tracking and file management.
* [Kolab](https://kolab.org/) - Another groupware suite.
* [SOGo](https://www.sogo.nu/) - Collaborative software server with a focus on simplicity and scalability.
* [SOGo](http://www.sogo.nu/) - Collaborative software server with a focus on simplicity and scalability.
* [Zimbra](http://community.zimbra.com/) - Collaborative software suite, that includes an email server and web client.