I had an issue on-site recently, after configuring Azure AD Connect and Exchange hybrid and successfully migrating some mailboxes I got the following error migrating a few mailboxes – “Error: InvalidRecipientTypeException: Unsupported recipient type ’Mailbox’ provided. Only ’Mailuser’ is supported for this migration type.”
On further inspection I realised that these users previously existed in Exchange online while the customer was “testing” Office 365..
When I assigned a license to user, it seemed to re-attach the mailbox therefore having the RecipientType UserMailbox and not the required MailUser.
I first removed the license and re-assigned it but the same result – UserMailbox, I then removed the user from the sync by moving it to an OU that was not included – forced the sync using Synchronisation Services Manager until disappeared from O365, then re-added it and forced the sync again.. When I had done all that and reassigned the license the result was the same UserMailbox… frustrating.. I needed to somehow purge the mailbox so it didn’t get re-connected..
I finally found the following solution to be the following:
- Removed the license from the user
- Remove the user from the Azure AD Connect sync
- Force Synchronisation
- Once the user has disappeared from Office 365 run the following command :- Remove-MsolUser –UserPrincipalName Desk1@domain.com –RemoveFromRecycleBin –Force
- Re-add the user to Azure AD Connect sync
- Re-assign licence
- Run Get-User and confirm the user is still MailUser and not UserMailbox
You can now successfully move the users mailbox!