Welcome to WebmasterWorld Guest from 188.8.131.52
As far as receiving the mail and parsing...well, that's out of your control. The recipient's server determines how to handle the mail, not you.
You could, if you have access to the server that you host on, edit the aliases file (on unix) and point a email address to a perl file, use the perl file to read any values and arguments, and then use that to pass to PHP.
I thin this is a very basic outline of how it can be done, but I think that it is a possibility.