When your account is created, a master POP3 account is set-up by default for the username that is assigned for your Web Hosting account.
This account is firstname.lastname@example.org and this name cannot be changed. In your Control Panel, you will notice that this POP3 account is "locked". While you cannot delete it, you can change the password for it at any time.
It is not recommend to use the "master" email account for general email. It should be used to receive messages from the Web Hosting account only.