If you need to open an additional mailbox, follow the steps below:
Open Outlook At the top right-hand corner, find and click on your initials.
A small window will pop up. Find and click where it says “open another mailbox” at the bottom.
Begin typing the email address connected to the second mailbox you wish to open. Autofill may find the email address you’re seeking before you’ve typed the entirety out. Once you have selected the correct email address, click “Open,” and you’re done!