Office 365 - Outlook - Open and Use a Shared Mailbox on the Web
Information and a link to Microsoft Support about how to open and use a shared mailbox in Outlook on the web.
A shared mailbox makes it easy for a group of people to monitor and send email from a public email address, like email@example.com. When a person in the group replies to a message sent to the shared mailbox, the reply appears to come from the shared address, not from the individual person. You can also use the shared mailbox as a shared team calendar.
*Need more help with Outlook? Then check out the Microsoft Support website for Outlook help & learning.