So the complaint is... that he's getting a missed call email, when a call is successfully forwarded to his mobile. If it were going elsewhere, someone else's phone, then there may very well be a desire to know that they missed a call in the event it was never answred at the destination. Since it is being forwarded to the persons mobile, I'm not sure I understand why the Ring My Mobile option would not be used. After all, that is why it exists, and you don't have to think about activating it, when leaving the office.