Outlook for Mac does not support Auto-mapping of shared mailboxes.
After you have granted access as a delegate to a shared mailbox, you can add that mailbox to your auto-open list.
From the Outlook Client App:
- On the Tools menu, click Accounts > Advanced > Delegates
- Under Open these additional mailboxes, click the [+]
then specify each mailbox you want to have open when using Outlook
- Click the OK button to save your changes.