409454 create email forwards thru api

Hi I have several domains hosted on my dedicated server. I'm planning to sell email accounts for those domains ... and for that i want to create a website... where in user comes to it and types the needed email username, and selects domain, and enters is current email address and clicks submit. on click of submit: the script should first check for the email username availability, then if its available it should create theat email a/c as a forwarding email a/c which is set to user's current email address. for this we are going to charge customer a nominal fee anually which shall be integrated thru ippay payment gateway.