Remove flag for awaiting migration

Hi there,

I#m just supporting a customer who is trying to setup his full environment after a cyber attack. There was a hybrid deployment with some few migrated Exchange mailboxes, but all AD accounts synced to cloud.

So we already removed the AD Sync and the AAD accounts turned into cloud only accounts. But in Exchange for the majority all the users are still mail users although they have an assigned Exchange Online Plan 2. We already tried to remove the license and re-assign it again, but the object still remains as mail user.

There is a way how we can turn the user the mail user to mailbox user, but therefore we have to remove the mail user and restore the MSOLuser from the recycle bin. This is not the best approach, because we have to set a new password. What sounds pretty easy is a real pain, because we have to provide several thousand passwords to distributed users.

We would like to keep the passwords in the first steps and enforce the password change at logon.
I guess there must be a flag or an attribute which still keeps the information that the object is waiting for a mailbox migration from on-premises.

Is there a possibility to clear this attribute so that we could enable the mailbox right away without setting a new password?

Thanks in advance.

Kind regards,

woelki