Forum Discussion
Enable AD Connect sync with existing Office 365 accounts and mailbox
Hi, I'm managing an Office 365 tenant with 60 users with E3 subscription. For the moment all users have a username with @mydomain.onmicrosoft.com domain and a mailbox associated. Now, I want ...
You should have done the directory sync before you started the mailbox migration.
The easiest way to do this for 60 users is described at https://support.office.com/en-us/article/use-minimal-hybrid-to-quickly-migrate-exchange-mailboxes-to-office-365-fdecceed-0702-4af3-85be-f2a0013937ef?ui=en-US&rs=en-US&ad=US
But since you did not do that, see https://support.microsoft.com/en-us/help/2641663/how-to-use-smtp-matching-to-match-on-premises-user-accounts-to-office to get these cloud accounts connected to the on-premises accounts