Email message -> php object?

I'm trying to take a file containing a complete email message, including headers and turn it into an object which I can use to get/change various bit of information about the message.

I've found a few bits and pieces online that let you create a mail-type object from seperate subject/headers/from/to etc but not one that creates it from a complete raw email.

Has anyone got any ideas where to look for this or done something similar?

Cheers!

EDIT: php 4.1.2 on Debian Woody.