Meeting duplicated thousands of times and is preventing free/busy information from being shared.

Said A 706 Reputation points

Hello everyone,

I have a user B that tries to set up a meeting with user B. But, free/busy information for User B always show as unavailable (greyed out).

By doing the free/busy test over here:

I get the following error: 5006 The result set contains too many calendar entries.

I tried connecting to the mailbox on the Outlook client and found a meeting entry that is duplicated almost 10 thousand times. Tried to delete them, the mailbox worked momentarily but the duplicated meeting came again. (in less than 24 hours)


  • the mailbox is under a litigation hold (this shouldn't prevent us from deleting calendar entries)
  • the user mailbox is hosted on Exchange Online although we have a Hybrid Exchange setup
  • I have found multiple articles mentioning a way to delete the meeting entries using MFCMAPI, but either the steps are not clear and I don't want to delete anything else other than that particular meeting.

I would appreciate any help.

Outlook Management
Outlook Management
Outlook: A family of Microsoft email and calendar products.Management: The act or process of organizing, handling, directing or controlling something.
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  1. Joyce Shen - MSFT 16,641 Reputation points

    Hi @Said A

    According to your description above, your issue is like the problem introduced here: You can't view free/busy information on another user's Calendar in Exchange Online

    This issue occurs if the user's calendar has a time slot that contains more than 1000 entries. And the solution to this issue is that we need to delete the items from the user's calendar.

    I would like to confirm which method did you use to delete the items?
    Litigation Hold is an Exchange server future that enables us to “freeze” all the mail items that were deleted by the user and keep this mail item in a hidden folder that can be accessed by the Exchange administrator.

    Here you could try other ways to remove these items:
    How to Use PowerShell to Remove Calendar Items from Exchange Online
    Please Note: Since the web site is not hosted by Microsoft, the link may change without notice. Microsoft does not guarantee the accuracy of this information.

    If the duplicated meeting still come again, you could check the mailbox audit log to find more information: Manage mailbox auditing

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    1 person found this answer helpful.

  2. Said A 706 Reputation points

    Issue solved using MFCMAPI,

    I followed the steps mentioned in the link below:

    It took a while for the mailbox to pick up the changes and free/busy information was accessible for other users eventually.


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