New Shared Mailboxes are not Appearing for users in Outlook classic

Question

I created a shared mailbox for 30+ users to access daily earlier this week. It's the end of the week and users using Outlook classic are still not able to access the mailbox. Their other existing shared mailboxes are accessible and updating fine with new mail and other changes. New mailboxes are not appearing unless switching to New Outlook or accessing Outlook OWA (easier said for sure.)

Answer 1

The method produced by the ai assist has been attempted and failed to bring into Outlook classic multiple times.

Answer 2

Dear @Justin M, 

Good day, and I appreciate the clear explanation of your concern.   

Classic Outlook for Windows uses Autodiscover and auto‑mapping to automatically add shared mailboxes once Full Access is granted directly to a user. If access is assigned through a group, the mailbox will not auto‑map. Even with correct permissions, Classic Outlook may take some time to refresh and the mailbox may appear only after Outlook is restarted and changes finish syncing. 

Please see the following workarounds that will help you verify the issue:  

Step 1: Confirm how Full Access permission was granted 

If access to the shared mailbox was granted through any type of group, including a mail-enabled security group or Microsoft 365 group, Classic Outlook won't auto-add the shared mailbox.  

• Auto-mapping only works when Full Access is assigned directly to individual users. 

If the shared mailbox was assigned using a group, this explains why it doesn't appear automatically in Classic Outlook, even though it is accessible in New Outlook and OWA. 

Step 2: Refresh auto-mapping on the admin side if permissions are correct 

If Full Access was already granted directly to individual users, Outlook classic may still be using outdated Autodiscover data. In this case, removing and re-adding the permission typically forces a clean auto-mapping refresh. 

Please note that this action must be performed by your organization’s IT administrator. 

Try removing and re-adding the Full Access permission with AutoMapping explicitly enabled. Test with one user first using the following PowerShell commands: 

# Remove existing Full Access permission  
Remove-MailboxPermission -Identity "Shared Mailbox Name" -User "User's Address" -AccessRights FullAccess  

# Re-add Full Access permission with AutoMapping enabled  
Add-MailboxPermission -Identity "Shared Mailbox Name" -User "User's Address" -AccessRights FullAccess -AutoMapping $true 

After updating permissions, ask the user to fully close Outlook and reopen it. 

Please note that Outlook classic can take up to approximately 30 minutes to reflect updated Autodiscover or auto-mapping changes. 

Step 3: Contact Microsoft Support 

If the shared mailbox still doesn't appear after completing the steps above, I recommend that your IT administrator open a support request through the Microsoft 365 Admin Center > Support > Help & Support for further investigation. 

A technical support engineer can perform a remote session to investigate the situation, verify the backend configurations, and run any necessary synchronization tools to resolve the problem. If the issue requires further attention, they can escalate it to a specialized team for deeper analysis.  

As a moderator, I don't have the tools to investigate your specific account directly because this is a user-to-user support forum. Moderators and contributors, including external Microsoft employees, cannot directly intervene in Microsoft product features or access back-end systems. Our role is limited to providing technical guidance on reported issues, requests, or ideas. However, I will try my best to guide you as clearly as possible.    

I hope this information is helpful. If you have any questions or need further support, please don’t hesitate to reach out at any time. 

Thank you for your patience and understanding. 

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Answer 3

In classic Outlook, new shared mailboxes should appear automatically once users are added as members and Outlook is restarted. If they do not, each affected user must manually add the shared mailbox to their profile.

Have users do the following in classic Outlook:

1. Close and restart Outlook once to see if the shared mailbox appears automatically in the Folder pane.
2. If it still does not appear, manually add it:
   1. Open classic Outlook.
   2. Select File > Account Settings > Account Settings.
   3. On the Email tab, ensure the correct primary account is highlighted, then choose Change.
   4. Select More Settings > Advanced > Add.
   5. Enter the shared mailbox email address (for example, ******@contoso.com).
   6. Choose OK > OK.
   7. Choose Next > Finish > Close.
3. The shared mailbox should now appear in the Folder pane in classic Outlook and update like the others.

If users can see and use the mailbox in New Outlook or Outlook on the web, membership and permissions are already correct; the missing step is adding the mailbox to the classic Outlook profile as above.

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References:

• Open and use a shared mailbox in Outlook