I migrated a mailbox from Exchange 2013 to Exchange Online, but a copy of the mailbox still remains on Exchange 2013 server. All settings in Office 365 show the mailbox and user are ok. User can access mailbox via Exchange Online WebApp but not via Outlook 2010 or 2013 client. There are no directory synchronization errors that I can see.
I do not want to delete the mailbox because it is live.
Any advice on how I can solve this? Thank you