If you've ever wanted to be able to send an email to an account and have PHP pick it up and parse it, this new post from Derick Rethans is exactly what you're looking for. It's based around the alpha release of a Mail component PEAR package, part of the eZ family.
Many PHP applications require to parse e-mail messages. For example bug systems and ticket systems that want to allow input by e-mail. For sending e-mail there are already decent implementations, ones that even allow sending multi-part and mixed text/html messages with attachments and so on.
He gives an example of how the component can be used to grab the mail from a remote POP3 server and display the parsed results with a few echo statements. Getting different values in the mail messages is made simple and is as easy as using structures like "$mail->to->email" or "$mail->body" to reference the content you want.