Adding an additional mailbox - Outlook (classic)

To add an additional mailbox in Outlook (Classic version) open Outlook and click on the File Menu.

From here click Account Settings and then on the drop-down menu which appears, choose Account Settings

On the Account Settings page, select your account and then click "Change" 

On the next window click the button for "More Settings"

Click the Advanced tab and then click Add

In the box that appears, enter the name of the mailbox you want to add and click OK as shown:

Untick the option to Download Shared Folders and then click OK

Click Next

Click Done

Restart Outlook and the mailbox will be located in the folder list on the left.