/Hosted mode or not /Hosted mode, that is the question … since Exchange 2010 SP2, recomended not !
“If you haven’t yet deployed Exchange 2010, our recommendation is to avoid /hosting mode and go directly to Exchange 2010 SP2 using the on-premises configuration. This will allow you to offer the features customers are looking for, and avoid a cross forest migration down the road.”
Future of /Hosting Mode
https://blogs.technet.com/b/exchange/archive/2011/10/13/future-of-hosting-mode.aspx