Zentyal 2.0 Feature List (Formerly known as ebox)
I was looking for an open source solution to replace microsoft exchange e-mail server, and came across this project. It actually handles the requirement and a lot more. I am still exploring, but it looks very interesting for a “network in a box” solution. It runs on top of Ubuntu 10.04 server, which were already running so it was easy for us to install and test out.