PHP Tips & Tricks
Preventing email header injection
http://www.swiftmailer.org/ - get swift mail
http://phpsense.com/php/php-mail.html - nice writeup explaining how header injection works, and basic use of phpmailer and swift mail
http: - PHPMailer user complaining about header injection
http://randomfoo.net/blog/id/4014 - Zero tolerance--a short script that bans attackers from the web site entirely
http://www.symfony-project.com/forum/index.php/m/16127/ - Extend PHPMailer with some header injection protection