Add additional mailboxes - Outlook 2013/2016
You can only add and open an additional mailbox that you have been granted access to.
- Click on File
- Click on Account Settings then Account Settings...
- Click on Change...
- Click More Settings...
- Click on the Advanced tab
- Click on the Add... button
- Type in the email address of the other mailbox and click OK
- Repeat Steps 6 and 7 for each additional mailbox required
- Once all mailboxes have been added, click OK
- Click on Next >
- Click Finish