tagline: From openSUSE
Kolab is a secure, scalable and reliable groupware server. It is formed by a number of well-known and proven components and adds intelligent interaction between them. There's a web administration interface, management of free-busy lists and resources, synchronization for several devices and more. Various clients can access Kolab, among them Kontact (KDE), Outlook (Windows) and Roundcube (Web). Best of all, Kolab is Free Software, so you are free to use, study, share and improve it. 
- The following functionality is provided by: email server, spam and virus filtering, webinterface.
- Kolab supports secure protocols as: imaps, https, smtps, https, etc.
- The web interface can be used to add, modify and remove users, domains, distributions list, shared folders, among other things.
Tips and tricks
See SDB:Kolab for tips, tricks and detailed installation instructions.