I need to be able to allow a user to fill in his/her e-mail address up to the domain part i.e. "@hotmail.com" on a webpage. The part that they filled in must also be valid e-mail characters. This means that they can only fill in their first part of their e-mail, and they can only belong to a certain domain. Is this possible? Do I use regular expressings or a mask control. And how to do it is the question!