Iv'e just been reading horror stories and it seems its best not to respond at all since that tells them it's a working email address. They seem to see the people who are on to them as potential victims to extort. Next thing you know your email account just sent out thousands of death threats like this idiot.
http://www.scamorama.com/joesmith_mcboll.html
Don't go poking sticks into bees nests.