Forum Discussion
The question nobody dares to ask! How do you create a new user in a hybrid environment.
The best practice is whatever works for your user management workflows. You can create it either way. In a hybrid you can move mailboxes back and forth whether they were created on-prem or in the cloud.
One caveat with New-RemoteMailbox is that it can't do Shared mailboxes. Those you need to create on-prem and then move, or, create in EXO as a user mailbox and then convert to Shared. Either way, same result.
I did some extensive testing and research on this topic. I have elected to create new user, room, and equipment mailboxes in Exchange Online. My process for user, room, or equipment mailboxes includes:
1. Create AD account and add sync attribute.
2. Run enable-remotemailbox command
3. Wait for synchronization.
4. License mailbox.
I am creating shared mailboxes on-prem and migrating them.
In the event you need to migrate a mailbox created in Exchange Online back to on-prem you will need to add the mailbox GUID as shown in this article:
https://support.microsoft.com/en-us/help/2956029/-migrationpermanentexception-cannot-find-a-recipient-that-has-mailbox-guid-guid-error-message-when-you-try-to-move-a-mailbox-in-an-exchange-hybrid-deployment
I hope that helps.