SOGo

When you are working in a group of likeminded peoples you need to share your files and information, at that time SOGo will help you. It is actually a groupware server where you can share anything from contacts to emails and files etc.

SOGo is a fully supported and trusted groupware server with a focus on scalability and open standards. SOGo is released under the GNU GPL/LGPL v2 and above.
Source

Download Here