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Unable to access shared mailbox

Anonymous
2025-05-21T12:02:17+00:00

Hi,

I am trying to access a shared mailbox but I do NOT have access, while my colleagues DO have access to it.

I have received the following errors:

  1. When I try to open the shared mailbox on the web, I get the following error:

Error 500

err: Microsoft.Exchange.Data.Storage.MailboxUnavailableException

estack: Microsoft.Mapi.MapiExceptionUnknownUser

emsg: ErrorPermanentStorage

  1. When I added the shared mailbox in my new Outlook, I get the following error when I try to open the folders:

You might not have permission to perform this action.

  1. When I added the shared mailbox in classic Outlook, I get the following message:

Cannot expand the folder. The set of folders cannot be opened. The attempt to log on to Microsoft Exchange has failed.

  1. I have tried to repair the ost file using the Microsoft Outlook Inbox Repair Tool. It gave me the following message when I tried to launch the scan:

The Microsoft Outlook Inbox Repair Tool does not recognize the file ***ost. No information can be recovered.

Could the experts advise me how to get access?

Outlook | Windows | New Outlook for Windows | For home

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  1. Anonymous
    2025-05-21T13:25:08+00:00

    Dear Chandeni, 

    Good day! Thank you for posting on Microsoft Community.

    I apologize for the experience you have had with this issue. Kindly try the following suggestions to resolve: 

    1. Verify User Permissions 
      • Make sure that your account is granted Full Access (Read and Manage), Send As or Send on Behalf permissions
      • Your Admin could grant shared mailbox access to your account by using Exchange Admin Center  Image
      • If you've already had access to the shared mailbox, your Admin could try to remove your access, then grant you access back.
    2. Try Accessing via Incognito Mode 
      • Open Outlook Web in Incognito/InPrivate mode
      • Use Open another mailbox from your profile icon
    3. Clear Browser Cache or Try Another Browser 
      • This helps check if the problem is coming from your browser or device

    I hope this information is helpful. If you have any further questions or concerns, please don't hesitate to reach out. 

    Best regards,  

    Doris V - MSFT | Microsoft Community Support Specialist

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