Office 365, Outlook for Mac, Add shared mailbox
Offices often have at least one shared mailbox for voice mail, responding to outside inquiries, projects, and more. Follow the steps below to add a second account to Outlook 365 on a Mac computer. Note: if you do not have access to this email address, the process will fail. Your department office manager should request access on your behalf.
Go to the Outlook menu and choose “Preferences”
Select the + (plus) sign to add a new account
Type in the shared mailbox address and select "Continue"
When prompted to Sign In, replace the email address with your own and choose "Next"
Enter your own NetID and password
When it tells you the account has been added successfully, you can close that window. It will be at the bottom of the folder list in the left-hand navigation pane.