Add additional mailboxes - Outlook 2013/2016/2019

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 on 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