Great post from Microsoft Exchange Team talking about certificate requirement in Exchange Server 2016 and comparison between the new version and Exchange 2010.
If you are like the vast majority of our customers, you already have some version(s) of Exchange deployed in your environment. Depending on the version, you may have different namespace requirements today.
Read more at source: http://blogs.technet.com/b/exchange/archive/2015/10/06/namespace-planning-in-exchange-2016.aspx
