If you are seeing an error window with the following message: "Remote Desktop Connection cannot verify the identity of the computer that you want to connect to." then you need to install the more recent version of Remote Desktop Connection for Mac.

The more recent version is available here: https://itunes.apple.com/us/app/microsoft-remote-desktop/id715768417

Unfortunately this issue occurs because the Microsoft Office environment installs an outdated version of the RDP application that does not work with Windows Server 2012.