In order to circumvent the harvesting of email addresses from a page, many web designers are putting form mailers into their pages. Sadly, most aren't taking security into account, and it is just adding to already monumental Spam problems.

The biggest problem is with Header Injection. There are a ton of good articles on the web about how to keep malicious users from injecting headers with a mailer script. Just run "php mail header injection" through a Google search, and you will find some. (more...)