Well, the migration problems are growing by leaps and bounds.
Some brainiac setup our domain forrest as kimray.org. Yet our email is kimray.com. In the move to Office 365 for our email the network Active Directory guy changed everyones UPN or login id from
user@kimray.org to
user@kimray.com. When I asked about dong this years ago I was told changing the login ID would screw all kinds of things that use active directory for user authentication.
Well...It's Happening!!!