if(eregi('warwick\.ac\.uk', $_POST['registrant_email']) && (strlen($_POST['registrant_email'])>0)) {
	  $_POST['registrant_email'] = quote($_POST['registrant_email']);
} else {
  $_POST['registrant_email'] = NULL;
  $message .= "<tr><td>email address must be in the format @warwick.ac.uk</td></tr> ";
}