/* Custom */
    add_filter( 'wpcf7_validate_text', 'xyz_validation', 20, 2 );

    function xyz_validation( $result, $tag ) {

        $email = isset( $_POST['your-email'] ) ? trim( $_POST['your-email'] ) : '';
        $subject = isset( $_POST['your-subject'] ) ? trim( $_POST['your-subject'] ) : '';

        if ( !empty($email) || !empty($subject) ) {
          $result->invalidate( $tag, "Really nigga?" );
        }


      return $result;
}