When a mailbox is approved in Dynamics 365 online connected to Exchange online with the global administrator approval, there isn't any auditing recorded within portal.office.com, portal.azure.com, or protection.office.com/unifiedauditlog.

It would be nice for more visibility of the global admin approval outside of Dynamics and auditing the activity of the application against the user's Exchange mailboxes. This is needed for auditing and compliance and should be stored in a central location such as Azure.