Adding Additional Mailboxes in Outlook This document provides a step-by-step set of instructions on how to add additional mailboxes in Outlook 2010 or 2013. From the Outlook menu bar, select File . Select Info, click Account Settings, select Account Settings . Select your default account and click Change . Click on More Settings . Select the Advanced tab and then click on Add Enter the name of the additional mailbox into the Add mailbox field and click on OK . NOTE : if there is more than one potential match, choose the correct option in the dialog box and select OK Click on Next , click Finish , click Close . The additional mailbox has been added to Outlook. It will appear in the Outlook navigation pane.