On the email headers look for the originating IP and the last IP it was sent from and you will be able to know the source..However, you will find the IP is for an ISP or is from Internet based email services e.g yahoo, gmail etc....Once you get the IP, then you would need to use legal means for the ISP etc to trace from there network...It's not easy...
Hardwork, Smartness & Humility = Successful and Happy life...Jipange sasa hivi