I have recently built out an Exchange 2013 server to migrate to from our existing Exchange 2010 set up. After installing, patching, and configuring the new Exchange 2013 server, I noticed that 2010 still had Unified Messaging enabled and available, but I could not enable it on Exchange 2013. I have attempted to run the newest copy of the installer to see if I missed a feature installation, but I cannot find it. I can enable/disable UM on the 2010 server, but no luck with the 2013 server. I am posting some of the details about my deployment below.
Exchange 2010 Standard:
Host OS: Server 2008 R2
Version: 14.3 (Build 123.4)
Exchange 2013 Standard:
Host OS: Server 2012
Version: 15.0 (Build 516.32)