Please don't do that, for two reasons. 99.8 percent of the email addresses in the "From" line in spam do not belong to the spammer. Spammers routinely use bogus addresses in the "From" line or even forge the email addresses of innocent bystanders there to misdirect complaints. It is trivially easy to forge the "From" line of an email header.
Also, every time you reply to a spam, the spammer knows your email address is a live one, and they will sell it to other spammers.
Want to reduce your spam load? NEVER reply to a spam and always trace the point of origin of the spam and the URL (if any) they are advertising, then complain to the abuse coordinator or postmaster at those domains. Spamcop.net provides a great free service that does just that.
BTW, how did that cornstarch thing work out for you?
Regards,
L