Form being filled out automatically....

I've got a problem. I have a form that the user fills out and then hits submit on and it sends an e-mail. My problem is that I have one AOL user that claims that when ever he goes back to the form, it doesn't present the form - it just sends the message. It appears that for some reason $HTTP_POST_VARS["EMAIL"] has a default value or it's a cache issue. Any ideas???? Here is the psudo-code... if( ! isset( $HTTP_POST_VARS["EMail"] ) ) { <form method="POST" onsubmit="return validate(this)" name="MailForm"> // Rest of form stuff } else { // send message here }