There is an API that can retrieve all emails from shared mailbox https://graph.microsoft.com/v1.0/users/{sharedmailboxmailaddress}/messages. However, I am not sure if this can take filter criteria to refine the messages that match certain criteria? for Eg. only pick messages that are received from a specific mail address https://graph.microsoft.com/v1.0/users/{sharedmailboxmailaddress}/messages?$filter=sender/emailAddress/address eq ‘[email protected]’