Exchange and Office 365 Duplicate Account

[Bankesy]

Good morning,

 

Somehow I have ended up with a user who has a mailbox on both the Exchange server on site and Exchange online, is there anything I can do to fix this without losing data so I'm just left with one mailbox for the user in 365?

 

All ideas welcome.

 

Thanks

[robintech]

https://learn.microsoft.com/en-us/exchange/troubleshoot/user-and-shared-mailboxes/mailbox-exists-exo-onpremises

 

says you can copy the data to the online one if you have Exchange Server 2013 or later