Store their email data into a variable:
$email = $_POST['email_field_name'];
Then validate it using:
if (filter_var($email, FILTER_VALIDATE_EMAIL)) {
//if the if statement executes, this means it is a valid email address....
}
else{
echo "The email you entered was invalid. Please try again. You will be redirected shortly...";
header("refresh:5, url=your_form_page.php");
}
Then just do exactly the same as you have done for the email to be sent to you, but just write code to assist their email address as such:
$mailTo = $email;
Hope this helps somewhat.
Kind regards,
Labtec