Upcoming changes to license re-assignment in Exchange Online

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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:

  1. 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.
  2. 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  • For a hybrid user, the mail user is not converted to a cloud mailbox because it is assumed that the license was revoked because the user was off-boarded from Exchange Online.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.

New behavior

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 any previous mailbox content. If the license is reassigned within 30 days of revocation, then mailbox content will be restored.

Exchange Online Team

Read full article (Microsoft Exchange Blog)

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