Matt is correct here. If you try to install it on Windows Server 2012 Standard it will fail to complete. But if you install it on R2 it will work I would just use the most updated version you can. But I don't recommend setting up a new environment on an EOL OS. You should try to get on something newer as the longer you sit on that the more liability that will carry.
Zach Sylvester
Software Developer
SmarterTools Inc.
www.smartertools.com