Exchange Connection Problems

Fix Cannot Open a Shared Mailbox in Outlook on the Web

Maira Mehtab Oct 20, 2026 868 views

Question details

Users are unable to access a Microsoft 365 shared mailbox through Outlook on the web due to permission errors or server exceptions.

How to Fix Cannot Open a Shared Mailbox in Outlook on the Web

Product: Outlook on the web (Microsoft 365)
Device & OS: not provided
Scenario: Attempting to open and view a shared mailbox using the Outlook web interface.
Observed behavior: The shared mailbox opens successfully in the Outlook desktop application but fails in the web version, often displaying errors such as WrongServerException or ErrorMailboxFailoverWithoutRedirection.

Before you start

Ensure you have a stable internet connection and verify with your IT administrator that your account has been granted explicit 'Full Access' permissions to the shared mailbox.

Solution 1Recommended

Verify Permissions and Clear Browser Cache

Resolve local browser caching conflicts and confirm you are utilizing the correct method to access the shared mailbox.

Often, shared mailboxes fail to load on the web due to corrupted browser cache data or because the mailbox wasn't opened using the correct 'Add shared folder' procedure.

Open via Add Shared Folder

Log in to Outlook on the web. Right-click on 'Folders' in the left navigation pane, choose 'Add shared folder', type the name or email address of the shared mailbox, and click 'Add'.

Test in Private Browsing Mode

Open a new Incognito or InPrivate browsing window (Ctrl+Shift+N on Windows). Log into your Microsoft 365 account and attempt to access the shared mailbox to bypass local caching.

Clear Browser Cache

If the private window works, return to your normal browser window, press Ctrl+Shift+Del, select 'Cached images and files' and 'Cookies', and clear the data. Restart the browser and log in again.

Permission Propagation Time: If you were just granted access to the shared mailbox, it can take up to 60 minutes for the permissions to fully propagate across Microsoft's Exchange servers.

Solution 2

Submit a Microsoft 365 Service Request

Escalate the issue to Microsoft Support if server-side exceptions like WrongServerException persist.

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Frequently Asked Questions

Why does a shared mailbox work in the Outlook desktop app but not on the web?

The Outlook desktop app uses different connection protocols and often caches mailbox data locally, which can mask server-side routing issues. Outlook on the web relies on real-time server connections, making it more susceptible to web cache conflicts and Exchange server routing exceptions like WrongServerException.

How long does it take for shared mailbox permissions to apply in Microsoft 365?

After an administrator grants 'Full Access' permissions to a shared mailbox, it typically takes between 15 to 60 minutes for those changes to replicate across all Exchange Online servers. During this time, you might see permission errors in Outlook on the web.

What does WrongServerException mean in Outlook on the web?

A WrongServerException error occurs when Outlook on the web attempts to route your session to the wrong backend Exchange server where the shared mailbox is not actively hosted. This is usually a Microsoft 365 backend issue that requires an administrator to open a support ticket.

Outlook & Email Problems