function reset_phpmailer_instance() {
  $mailer = tests_retrieve_phpmailer_instance();
  if ( $mailer ) {
    $mailer             = new MockPHPMailer( true );
    $mailer::$validator = static function ( $email ) {
      return (bool) is_email( $email );
    };

    $GLOBALS['phpmailer'] = $mailer;
    return true;
  }

  return false;
}