Zimbra

http://www.zimbra.com

http://www.zimbra.com/community
http://www.zimbra.com/community/documentation.html
http://wiki.zimbra.com
http://www.zimbra.com/forums
http://www.zimbra.com/blog

http://en.wikipedia.org/wiki/Zimbra

http://www.zimbra.com/downloads
Zimbra Collaboration Suite (ZCS)

Unified communications

http://www.zimbra.com/products/unified-messaging.html

Discussion

http://www.theregister.co.uk/2013/07/15/vmware_sells_zimbra_to_telligent/
http://blog.zimbra.com/blog/archives/2013/07/telligent-acquires-zimbra-from-vmware.html
http://blog.zimbra.com/blog/archives/2013/08/zimbras-commitment-to-open-source.html
http://www.unixmen.com/install-zimbra-collaboration-suite-8-6-0-centos-7
http://opensource.com/business/15/2/open-source-market-landscape
http://www.unixmen.com/install-zimbra-collaboration-suite-in-ubuntu