Outlook - The mailbox isn't available. This may have occurred because the license for the mailbox has expired.

MC222773 - Microsoft has made a change to Exchange Online in order to correct the way unlicensed mailbox access is handled. This change may cause Shared mailboxes to be inaccessible due to a license expired error.

The mailbox isn't available. This may have occurred because the license for the mailbox has expired. To find out how to gain access to this mailbox again, contact the person who manages your email account.

Outlook Shared mailboxes inaccessible due to license expired error.PNG
Outlook Shared mailboxes inaccessible due to license expired error
Users can ignore this if not experiencing the license expired error message.

⚑️ What is the impact ?

Delegates who access shared mailboxes might no longer have access to the mailbox. This occurs because both On-Prem AD as well as Azure AD see the mailbox as Shared, but Exchange Online still sees the mailbox as a User mailbox.

⛏️ How to resolve and fix ?

If you are experiencing the error message that the license has expired and the mailbox is showing as a shared mailbox in both On-Prem AD and Azure AD but in Exchange Online it is not a shared mailbox, run the following cmdlet using Exchange Online PowerShell
You may need to contact your Office 365 Tenant Admin to prevent or fix this issue.

Set-Mailbox -Type Shared


  • I got this today and the error was solved by itself. Strange.
    anon 22 Dec 2020 11:22:31 GMT
  • Try reassigning the license (like Exchange Online Plan 2). Had this happening with OWA for one of my customer and was fixed after resassigning the license.
    anon 03 Dec 2020 04:09:16 GMT
  • I get this error when accessing my colleagues mailbox via OWA who has left the company, the mailbox is mapped to my Outlook. Interestingly it worked fine from Outlook for a while and then started giving same message. The mailbox is not a shared mailbox.
    Should I convert the mailbox to a shared one?
    anon 06 Nov 2020 12:53:23 GMT
  • Tip for Exchange Admin - Ensure you have allocated Exchange license to the user in Exchange Online.
    Use this script to get and check all users with mailbox but no Exchange license

    get-mailbox | where {($_.recipienttypedetails -ne β€œDiscoverymailbox”) -and ($_.skuassigned -ne β€œTrue”)} | ft name,skuassign*

    Reference link - https://johnyassa.blog/tag/the-mailbox-isnt-available-this-may-have-occurred-because-the-license-for-the-mailbox-has-expired/
    anon 28 Oct 2020 09:27:03 GMT
  • Such errors auto resolve for Microsoft products and they close support ticket without SLA. move over to other services.
    anon 03 Oct 2020 21:34:11 GMT
  • This may occur when user is migrated from On premise Exchange to Office 365, users may not be able to access mailbox from OWA (office web apps)
    anon 22 Sep 2020 20:00:13 GMT
  • Further comments disabled!
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