Outlook can access only one primary mailbox. The example will show you how to set up Outlook to open two mailboxes.
First, set up Outlook with VIPuser1.Smarthust@vip.com.
Second, in VIP.com domain, locate the VIPuser2.Newton user account and assign the Full Mailbox Access right to VIPUser1.Smarthust.
Third, in Outlook, right click VIPuser1.Smarthust mailbox and select properties, locate "Open these additional mailboxes". Then, you will get the similar outlook layout shown below.
