NEVER answer to these emails..if you do,they'll understand that your email is active(at the beginning, they don't know cause they randomly choose email addresses) so don't answer...
another thing you can do is when you send emails,don't write your email address as they have programs that are able to read addresses on the net.. write them adding something xtra in this way: for e.g if your email were
[email protected], you could write charlesNOSPAM.at.dot.com... or
[email protected] and then write take away the 8's..