1. Log into the Customer Control Panel with your main account's username and password
2. Click on the Website Link.
3. Click on the Email link.
4. Click on manage mailboxes.
5. Select your domain name.
6. At the next page you'll see the list of email accounts you have, there you can click the "Delete" button next to the account you want to remove.
7. You've completed deleting the email account.