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How to FIX Microsoft Teams Error Mailbox Does Not Exist

Microsoft Teams have shared inboxes. These inboxes are accessible by an entire team and configured by the admin. A shared inbox can be added to Outlook and it also appears in the Microsoft Teams desktop app.

Microsoft Teams mailbox does not exist

A shared mailbox is an enterprise feature for Microsoft Teams and as such, it is an extremely complex tool that’s set up over an Exchange server. Configuring it isn’t easy and admins who set up a shared mailbox can practice fine-grain control over who can access it and the access can be revoked at any time.

If you were previously able to access a shared mailbox in Microsoft Teams, and are suddenly unable to access it, try the fixes below.

1. Ask admin for permission

It is possible that your permission for a shared mailbox has been revoked. Ask the admin to enable it again.

  1. Visit the Microsoft Exchange admin center.
  2. Go to Recipients in the column on the left.
  3. Select the Shared tab.
  4. Select a mailbox, and make sure your email address appears in the list of users who can access it.
  5. If the email doesn’t appear in the list, edit the mailbox and add it.

2. Check shared group permissions for Microsoft Teams

The Microsoft Teams shared mailbox can also be a shared group which essentially shows the same error if you’re unable to access it. Again, ask the admin to check that your user has permission to access it.

  1. Visit the Microsoft 365 admin panel.
  2. In the column on the left, expand Groups.
  3. Click Shared mailboxes.
  4. Select the mailbox that a user is unable to access, and add them to it.

3. Check for Exchange connectivity

Check if you’re able to, as a user, authenticate your credentials and connect with Microsoft Exchange.

  1. Open PowerShell with admin rights.
  2. Run the following command. Replace ‘yourDomain’ with the domain that your account is configured over e.g. https://mail.addictivetips.com.
Test-OAuthConnectivity -Service EWS -TargetUri <yourDomain>/metadata/json/1 -Mailbox <Exchange Online Mailbox> -Verbose | Format-List
  1. The results should be as below;
ResultType: Success
Identity: Microsoft.Exchange.Security.OAuth.ValidationResultNodeId
IsValid: True
ObjectState: New

4. Check OAuth connectivity

You should also check OAuth connectivity to make sure your system can communicate with the Exchange server. The test is run via a PowerShell command however, your user must have permission to run this command. This permission is set and granted by the admin on the Exchange admin panel.

  1. Open PowerShell with admin rights.
  2. Run the following command and make the following edits;
    • Replace ‘YourDomain’ with your Exchange domain.
    • Replace ‘Name of Mailbox’ with the name of the mailbox you’re trying to connect to.
Test-OAuthConnectivity -Service EWS -TargetUri "yourDomain/ews/" -Mailbox <Name of Mailbox> -Verbose | Format-List

Example

Test-OAuthConnectivity -Service EWS -TargetUri https://mail.addictivetips.com/ews/ -Mailbox "Team Inbox" -Verbose | Format-List

Conclusion

Shared mailboxes are an extremely complex feature. They exist with Microsoft Teams, and within Microsoft 365. Converting one from the other isn’t possible and it’s important to understand what type of mailbox you have configured before you add and access it to Teams. The “mailbox does not exist” error isn’t something an end-user can troubleshoot. If you see the ‘mailbox does not exist’ error in Microsoft Teams, let you system admin know and share these solutions with them.

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