well,
using cpanel, i was able to automatically create email accounts for clients during the registration process; however, i could never grab emails from those accounts using imap functions. i did sth wrong but never found a solution.
but here is what i learned.... no hosting provider will let you execute your own scripts (php, asp, you name it) that require root privileges. why? because of security reasons. so i do not think there are scripts out there that perform an operation like this at all. (except built in modules that have these capabilities like cpanel)
the solution? host your website yourself. at least this was my conclusion.
if you ever hear about a real solution please let me know.