Here’s an interesting article on Email Header Injection, a method spammers use to hijack your contact forms to send our mails. The article goes on to show how to protect the contact form from being abused.

It has become apparent that spammers are getting even smarter than we take them for. Rather than abuse open relays, which are almost non-existent, these scum-of-the-earth ‘traders’ are now abusing contact forms.

Link: Jelly & Custard » Email Header Injection in PHP