I stumbled across Zentyal which seemed to be quite an interesting Linux distribution. I say that as they claim to be able to replace Microsoft’s Small Business Server (SBS) and co-exist with Active Directory and Exchange.
Have a look at their website for all the features.
I wanted to install the guest additions after installing Zentyal in Oracle’s Virtual Box to run the virtual machine in full screen mode. This was not as straight forward as I though it might be. Below is a video tutorial that I created to show how to install the guest additions in Zentyal. (Watch in HD and full screen)
Also note: the links below the video are for the sites I used to get this working.