E-mails are only traceable to a person who is not trying to hide. You can trace e-mails from their headers but often times these are incomplete or have spoofed information. Also there are still mailers that allow annoymous mail/relaying which means once you get to that mailer you've really got no where else to go. (Unless the owner of the mailer feels like letting you paw through his logs which is not likely to say the least.) REMEMBER: The only thing a clever attacker needs to become anonymous is 1 compromised machine.

-Maestr0