If you find that some Outlook clients stopped connecting to the Exchange Online mailbox but OWA and ActiveSync is still connecting then check if modern authentication has been disabled for your O365 tenant To check run: Get-OrganizationConfig | Format-Table Name,OAuth* -AutoIf you find it is set to False and all your Outlook clients are 2013 or newer then enable it by running:Set-OrganizationConfig -OAuth2ClientProfileEnabled $trueYour disconnected users should start connecting within a few minutes.
One of my colleagues battled to migrate an on premise Exchange 2010 mailbox to Office 365. After trying to repair the mailbox and numerous other things he still received the below error: Transient error StoragePermanentException has occurred. The system will retry (6/640). Eventually he appended the -SkipMoving:FolderRestrictions to the New-MoveRequest cmdlet and managed to migrate the user’s mailbox to Office 365.