I am the coder who brought out the first cPanel email integration systems in php. I mean that. I can code your portal, cms, or simple website to allow your users to sign up for email in your cPanel shared account. The users can isntantly sign up for email, reset lost passwords instantly, and login to change their passwords instantly. I also include paypal ipn so that your users can pay you for the email service and they can even choose from a list of membership levels that you define. I can do Plesk email integration as well, but you need to be able to setup root cron jobs or else plesk will not allow the emails to be created. Plesk is just picky like that. Anyway, hit me up if you are interested. Most integrations are $99.99, some custom jobs have reached $399.99, but that is rare. I accept paypal too!