We currently have 3 domain controllers running Windows Server 2008 R2. We are using Exchange 2013 on premise (Version 15.0 (Build 1178.4)). I am planning the first step of adding a server running 2012 and promoting it to a DC on our way to getting the AD level eventually to 2016. I know that I will need to run adprep /forestprep and adprep /domainprep once I have the new server joined to the domain. My concern is with the effects this will have on Exchange 2013. In my research I have seen everything from "it can't be done" to "it's easy and doesn't break anything". Can the experts weigh in on what the expected and/or potential problems I need to watch out for are? Is there anything I can do to minimize the potential problems? If one of you have a step by step to offer I would be forever grateful but any advice is welcome. Thanks!