Shared mailbox in Exchange Online not auto-mapping for delegated users

Question

I’ve added Full Access permissions to a shared mailbox for a few users in Exchange Online, but the mailbox is not auto-mapping in Outlook for them. The permissions appear correctly in both the Exchange admin center and via PowerShell using Get-MailboxPermission. Users can add the mailbox manually, but it should appear automatically.

Answer 1

Hi @Lakin Marquieta

Thank you for posting your question in Microsoft Q&A forum. 

We understand that the user is able to manually add the mailbox, which confirms their permission level is correct. However, the auto-mapping flag might not have been configured or propagated properly.

To troubleshoot this, please try removing and then re-adding the delegate permission, explicitly enabling auto-mapping. You can refer to the command below, and we recommend testing it with one user first:

# 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 

Then, ask them to close and reopen Outlook to check if the issue still persists.

Please understand that our initial reply may not always immediately resolve the issue. However, with your help and more detailed information, we can work together to find a solution. 

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Answer 2

How did you add the permissions? If using PowerShell, make sure you specify the -AutoMapping switch, as it's not set by default. If you used the portal, it does set the flag by default.

Automapping relies on autodiscover, which in turn can take up to 30 mins or so to update on the Outlook (classic) client. If more than that has passed and you are still not getting the mailbox automapped, you should check for any autodiscover-related issues, both on the local machine (via the Test E-Mail Autoconfiguration tool) and remotely (via the ExRCA tool).

Keep in mind that hybrid scenarios (where one of the mailboxes is on-premises and the other one in the cloud) are not fully supported for automapping.