We just migrated a client from Exchange 2010 on premises to Exchange Online using the cloud only method. I currently have all the Exchange services disabled on the Exchange server and have new Outlook profiles configured for the O365 accounts and everything works fine.
The problem is that every couple of days a person or two will tell me they are being prompted for their credentials and their password is not working. When I look at their profile, it has reconfigured itself to point to the local server name. im not sure how a functional live profile just changes itself but im not sure where else to look.