Send as a shared mailbox that is hidden from the Global Address List

Outlook Desktop Client

Add the shared mailbox as a new account in Outlook by going to File/Account Settings/Account Settings. When prompted for credentials have the user sign in with their own credentials. After closing and reopening Outlook, the shared mailbox will be in the From dropdown list ready to use.

Outlook on the Web

To open the shared mailbox via the web add the shared mailbox address after https://outlook.office.com/mail/ example: https://outlook.office.com/mail/MailboxAddressHere@stlcc.edu Once the shared mailbox is open you can send as the mailbox.