Unable to add Shared Mailbox in Outlook Classic

DM 0 Reputation points
2026-10-06T18:42:42.9233333+00:00

User is able to see the mailbox both in OWA and in New Outlook, but when trying to add the mailbox in Outlook Classic, it takes forever until it eventually crashes. We have seen this behavior in several other cases. Only workaround so far has been to ask the user to use New Outlook, but not all of them like it and are very reluctant.
We have reinstalled the whole Office package, removed the account, created a new one, but nothing works.
I haven't been able to find any articles about this either.

Outlook | Windows | Classic Outlook for Windows | For business

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  1. Ryan-N 16,105 Reputation points Microsoft External Staff Moderator
    2026-10-06T19:06:28.9566667+00:00

    Hi DM,

    Welcome to the Microsoft Q&A forum.

    Based on your description, I understand that you can add the shared mailbox when using New Outlook and Outlook on the web. However, when you try to add the shared mailbox to Classic Outlook, the application becomes unresponsive.

    Additionally, you have already tried reinstalling Office, removing the account, and adding it again, but the issue still persists.

    First, please try opening Outlook in Safe Mode to determine whether the issue may be related to Outlook add-ins:

    1. Close Outlook completely.
    2. Press Windows + R.
    3. Enter: outlook.exe /safe
    4. Press Enter or select OK.
    5. Then, check whether you can add the shared mailbox and use Outlook normally.

    If the issue still occurs while Outlook is running in Safe Mode, and as you mentioned, this issue is affecting multiple users, I recommend contacting Microsoft Technical Support for further investigation.

    The support team can assist you with further checking your current environment and configuration to help determine the cause of the issue.

    To contact Microsoft Technical Support, you can refer to the following documentation:

     Get support - Microsoft 365 admin | Microsoft Learn

    I hope this information is helpful.

    If you have any questions or need further assistance, please feel free to share them in the comments on this post so I can continue to support you.

    I look forward to continuing the conversation.

    If the answer is helpful, please click "Yes" and kindly upvote it.

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  2. AI answer

    2026-10-06T18:42:57.6766667+00:00

    For classic Outlook, the supported path is:

    1. Confirm the user was added as a member of the shared mailbox.
    2. Close and restart Outlook.
    3. If the mailbox does not appear automatically, add it manually:
      • File > Account Settings > Account Settings
      • Email tab > select the correct account > Change
      • More Settings > Advanced > Add
      • Enter the shared mailbox address
      • OK > OK > Next > Finish > Close

    Since the mailbox already works in Outlook on the web and new Outlook, the mailbox itself and access are likely present. If classic Outlook hangs or crashes while working with the shared mailbox, one documented Outlook issue is shared mailboxes not automatically refreshing. The supported remediation is:

    1. Create a new Outlook profile.
    2. If avoiding a new profile, remove profile corruption from the current profile by deleting the 0102663e registry key under the Outlook profile.

    Important: editing the registry is high risk. Incorrect changes can cause serious problems. Back up the registry first.

    Registry path: Computer\HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Outlook\Profiles

    Steps:

    1. Right-click Start > Run.
    2. Type Regedit and press Enter.
    3. Go to the profile path above.
    4. Select the affected Outlook profile.
    5. In Registry Editor, use Edit > Find and search for 0102663e.
    6. Locate the key where the parent key is just above GroupStore.
    7. Delete 0102663e.
    8. Close Registry Editor and restart Outlook.
    9. Verify whether the shared mailbox now updates and opens correctly.

    If the issue continues across multiple users and multiple rebuild attempts, the practical next step is to open a support ticket, because the issue is affecting several users and persists after reinstalling Office, recreating accounts, and rebuilding profiles.

    References:

    AI-generated content may be incorrect. Read our transparency notes for more information.

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