Holy shit ! Those same assholes sent me email too. I reported them to the following agencies - I think you should do so immediately as well and then delete the email:
www.asacp.org
www.reportchildporn.com
www.missingkids.org
Also - do a who is and report them to the Dynamic DNS host that is holding their DNS info. I spoke with Tech support and they reported these guys to the FBI etc (there are international agencies equipped to deal with this). At the very least the company will eventually get all the accounts this company (idiots assholes whatever you call em) has and at least throw them off of their service. It may not stop em but it will put a dent in them for a while.
Another problem with these particular nasty assholes is that the have their own company set up to process their money - so no globill or CCBill or IBill to complain to. Sounds sophisticated, scary and makes you want to get a group of mercenaries and blow them the fuck up.