Spam bots search the websites and create mailing list to send the spam. They take the email addresses written on your website page in text format and send you spam emails. The spam bots are not able to read the email addresses written on a image (picture format). So to fool them Spam Proof eMail Generator have created a free service where you can just enter your email address, choose colors and font types and create a picture of your email address which spam bots will not be able to read. Check out the email image here which i have generated using this website.
Website: http://spam-proof-email-generator.com/