Change Auditor is not capable of reporting on when a mailbox is added to Outlook, however, if that mailbox has been added to the list of mailboxes being audited by CA, events will be created when a non-owner for that mailbox performs actions within the mailbox, such as:
Mailbox Opened by Non-Owner
Inbox Opened by Non-Owner
Message Read by Non-Owner
For a complete list of the Exchange events, please see the Change Auditor Exchange Event Reference Guide:
https://support.quest.com/technical-documents/change-auditor-for-exchange/event-reference-guide
