Opening a Shared Mailbox
Outlook Desktop
https://uwaterloo.atlassian.net/wiki/spaces/ISTKB/pages/1854013815
https://uwaterloo.atlassian.net/wiki/spaces/ISTKB/pages/1987445029/Adding+a+shared+mailbox+to+Outlook+for+the+Mac+-+Instructions+for+M365+Shared+Mailboxes.
Outlook Web Version
Sign in to your account in Outlook on the web. (https://outlook.office.com/)
On the Outlook on the web navigation bar, click the person “image” at the top right. A list appears.
Click Open another mailbox.
Type the email address of the shared mailbox, and then click Open.
Another Outlook on the web session opens in a separate window, allowing access to the other mailbox.
You may be required to log in again. Make sure you use your own username and password