we have a customer who is just onboarding Office 365 and they will start with the Exchange Online migration in some few weeks. Currently they are operating Lotus Notes.
From our side this customer only receives workshops and we try to show them how to change their mindset. The migration will be done by Microsoft. I guess it is MCS (Microsoft Consulting Services).
The customer has no good communication channel to Microsoft and they have received some disturbing information. So one week ago we had the status that the AD objects have been synchronized. Then our customer told us, hey we need now the mailboxes, so we showed them how to bulk assign the Exchange Online Plan with the group license templates.
Now Microsoft told our customer this won't work, they can not match the users for the migration, because they need mail users.
But as far as I know Enable-Mailbox is not available in the cloud, so how shall we or our customer enable an existing (synchronized) AD account as mail user?
To provision mail users in ExO, you simply need to make sure that the corresponding AD objects have proper values for the mail, targetaddress and mailnickname attributes on-premises. You should not assign Exchange Online licenses to such users prior to the migration, as that will provision an ExO mailbox.