Managing EXO365 Mailboxes – User Removal versus License Removal

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For Exchange Online 365 Messaging administrators, you may find that when an Exchange license is removed for an online user, the users mailbox is no longer available.  This is due to the user loosing their Messaging license and is by design.  There is also another scenario where a user is deleted, either in on-premises Active Directory with DirSync synchronizing this delete, which in turn removes the users mailbox.

Note – Mailboxes are maintained within Exchange Online 365 for 30 days before being purged, so if you are in one of these scenarios, the following will help explain how you can mange this:

Removed Users

Whether through On-premise deletion disablement or moved out of scope (DirSync Filtering), ECP mailbox deletion, Remove-Mailbox or Office 365 Portal.

  • These will be soft deleted and show up in ECPs Deleted Users as well as Office 365s Deleted Users UI and should be recovered through O365 Deleted Users UI
  • See for more details
    •  Note that if the user deletion originated on-premise through DirSync then recovery must originate there as well.

 License Removal

Managed through Office 365 Portal or O365/MSO PowerShell

  • This results in a “disconnected mailbox” this state is not viewable in any UIs the user looks like a standard User or MailUser.
  • Re-assigning the License will “reconnect” the mailbox automatically within 30 days, with the following caveats.
    • Up until late July or early August 2012, any unlicensed Shared/Resource/Room mailboxes would not be automatically re-connected upon re-licensing.
      • This has been remedied by blocking the disablement of these mailbox types on license removal so now when you remove a license for these “free” mailboxes the mailbox remains intact.
  • If an online user’s MailboxGUIDId does not match the online mailboxes GUID then automatic reconnection will not happen.
    • This was a bug, most typically exposed post v1 (BPOS) to v2 (Office 365) migration but other cases could expose it as well, bug is fixed pending deployment.
      • This issue can be solved by clearing the mailboxGUID value for the on-premise user, forcing a DirSync update and then adding the Exchange license.  Once done, the MBX should reconnect.

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