Add a Mailbox in Outlook 2016 for Mac

If you are a delegate and routinely respond to e-mail for someone else, you may want to add their mailbox to your account for quick access. You must have been granted at least Reviewer permission to open their mailbox and see it in your Folder List.

Add a mailbox to your Outlook folder view as follows:

Click on Tools > Accounts then select your Exchange account at left.
Click the Advanced… button in the lower right.
Click the Delegates tab.
Click the plus ("+") sign below the lower "People I am a delegate for" pane, then enter the name of the mailbox to which you have access. Click OK to select the mailbox.
Click OK to close the Accounts window.
The mail folders, calendar, contacts, etc for that mailbox should now be visible, assuming the owner has granted you delegate permissions.