setting up an automated email hosting service?

Hi

im looking to start an email hosting website/service.

Where users can signup and create their own myname@mysite.com (where mysite.com is my domain) are there any WP plugins that allow the automated creation of email accounts after user enter's a desired username.

Using either the existing hosting account's Webspace as the storage for the user's emails or if there some kind of re-seller services that give dedicated storage for each inbox (ideally something secure + economical)

Ideally it would be self automated so after user enters details and submits it will create everything and provide them with the account instantly.

If possible i need a simple and clean solution something visually nice like http://temp-mail.org/

Also if there are any nice wp themes that you recommend could work well with this ?

Thanks
Tom