That's a requirement for Piping.. but it makes it harder because your using cPanel, which like everything done their way. http://forums.cpanel.net/f5/mailparse-php5-64412.html
WHMCS isn't easier because you'd still be hit by the same issue...
When that's done all you need to do is this: http://screencast.com/t/D80upGpr
Well the demo stopped me due to the demo. Put your best off contracting to your host if you can't get Mailparse workiing.