Im not sure if there's a script on this but I want to make an email service NOT using a company like everone.net or anything something that someone registers and then I accept it and then they can use there account (not using my cpanel I can lose my account if I use that and someone spams)... so anything would be appreciated!

In my understanding for this to work you would have to have your own mail server and change the MX record on your domain to point to it. Unless you have a dedicated server (sounds like you dont) you wont be allowed.

If you did it would be pretty easy to setup a mailserver like Postfix, Mysql to store the users, and Squirrelmail for a good webmail client for your users. The actual scripts for creating users would be easy since its just adding them to mysql and the software all uses that for authenication. The problem is you would need root access to a server i believe to setup the mail server.