Forwarding Mail Dilemma 2

Is there any other way to forward all sent mail with it showing up in your sent box. I am under the suspicion that someone is using my computer after hours to send email with my email address on it and if I could forward all sent mail it would be helpful in procuring a login system with my company. I have tried creating message rules but none seem to automatically apply the rules to the sent box. I have asked a similiar question before and found no acceptable answers. I need a definite solutionto my problem soon. ANY IDEAS?????