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Can't access shared mailbox

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I just set up a new shared mailbox using powershell and the instructions listed here:

The mailbox was created successfully and I've created a security group and added members. I've also run the powershell scripts to grant them access. In OWA, when we go to "Open other mailbox" and start typing the name - it correctly autocompletes the name.

However, when we click "Open" we get the following error: A mailbox couldn't be found for If the problem continues, contact your helpdesk.

This happens for each user in the group, including myself as the administrator.

I've gone back into powershell to run the following command: Add-MailboxPermission "Northstar Shared Folders" -User sharedfolder -AccessRights FullAccess.

At that point it gives me a warning: WARNING: The appropriate access control entry is already present on the object.


All Replies
  • Hi B Kaz,

    Thanks for you post here. Based on the information you post, I understand that when you open an shared mailbox, you encounter an error message " A mailbox couldn't be found for If the problem continues, contact your helpdesk."

    The issue occurs if the permission wasn’t granted properly.

    To troubleshoot the issue, please refer the following steps:

    1.Connect to Windows PowerShell and connect to the service again.

    2.Assign yourself the FullAccess permission to access the shared mailbox. Run the following command:

     Add-MailboxPermission "Shared Mailbox Name" -User YourAlias -AccessRights FullAccess

    3.Assign the security group the SendAs permission to the shared mailbox. Run the following command:

     Add-RecipientPermission " Shared Mailbox Name" -Trustee YourAlias -AccessRights SendAs

    Note: Shared Mailbox Name is the name of the Shared Mailbox you were given. YourAlias is your alias for your account.

    For the detailed information, please refer to the following article about how to set up a Shared Mailbox.

    After this has been done, please wait a few hours (there is a downtime)and then check the result.

    Linda Wang

  • As stated previously, I tried re-running the Add-MailboxPermission and Add-RecipientPermission commands - but both commands gave me the warning that the access control entity already exists. I waited several hours and still receive the same message in OWA. I re-ran the permission commands again, but this time I used the usernames and not the name of the access group. We still cannot access the mailbox via OWA. However, the shared mailbox now shows up in Outlook for everyone and we can add/read/edit the folders from there. OWA doesn't work.

  • Hello B Kaz,

    You may need to submit a service request to our support team by log into the Microsoft Office 365 Portal from the admin tab on the left pane under support, select service requests. A support agent will be contact you to further assist you.  A remote session may be required. Feel free to update the post with any additional questions or concerns.

    Best regards,

    Sherika MSFT Support

  • There is not a service request option listed in our admin portal.

  • Hello B Kaz,

    I have sent you a private message.

    Please go to the Your Details section on the right side of the community site.
    Click Private messages.
    Click the subject title of the response to read the message.
    You can reply by using the form in this display.

    Best Regards


  • Hello B Kaz,
    How are things going? Did we answer your question to your satisfaction?

    If you have any other questions or concerns, please do not hesitate to contact us. It is always our pleasure to be of assistance.



  • Use my script, makes life easier.