Accidentally recreated Exchange 2010 mailbox after o365 migration

[utriainen]

Hello

Title tells problem, what would be best option to start using o365 mailbox again? 

This is AD with Azure AD sync, what would be easiest way to get o365 attributes back to AD user object? Using disable-remotemailbox and enable-remotemailbox poershell cmdlets souds extreme and can I even use them in this situation? 

[#2]

best to take backup of O365 mailbox first and then delete user from O365 ( considering user is not using other services such as One Drive) sync the user and then migrate the mailbox again.

[#3]

Not a option here.