In this post we want to highlight some upcoming changes around license re-assignment in Exchange Online to help admins get clarity on mailbox behavior and how license re-assignment works. The new behavior for re-licensed users will be effective from about end of March 2022, onwards.
Current re-assignment behavior
When an Exchange Online license for a user is revoked, the user object is converted to a mail user (MailUser). When a license is re-assigned to the user, one of two things happen, depending on the timing of re-assignment:
Exchange Online license re-assigned within 30 days after revocation. This is a straightforward scenario; if a user is assigned a valid license within 30 days of license revocation, their mailbox and all its data are reactivated.
Exchange Online license re-assigned more than 30 days after revocation. The behavior depends on the type of user:
For a hybrid user, the mail user is not converted to a cloud mailbox because it is assumed that the license was revoked because the user was off-boarded from Exchange Online.
For a cloud only user, the amount of time elapsed since revocation doesn’t matter; when the Exchange Online license is re-assigned, the user object is converted from MailUser to UserMailbox.
If the Exchange Online license is re-assigned even after 30 days, every user will have a mailbox assigned to them. With this change we are no longer assuming that the user was off-boarded after 30 days. Since the user had a mailbox when the license was removed, their mailbox will be reactivated after a license has been reassigned.
If after license reassignment, conversion of the recipient to UserMailbox was not intended, follow this process.
If license re-assignment happens after more than 30 days, a mailbox will be assigned, but it won’t have anyprevious mailbox content. If the license is reassigned within 30 days of revocation, then mailbox content will be restored.