Re: Jet
Its very unliely you would do an inplace upgrade of Exchange as the versions are generally tied to an OS, 2010 for example only works on 2008r2, 2013 on 2012r2 and 2016 on 2016.
The chances of something not working after an OS upgrade and Exchange upgrade is so large it would fall in to the category of seeing how much of a mess you could make of it and possibly AD as well. Apocolypse springs to mind.
Far better to just have good backups and migrate mailboxes to a shiny new server, no down time and nothing will break. Honest.
Biting the hand that feeds IT
