public function send($to, $subject, $message, $from = 'default', $headerExtra = [], $html = true) {
        if (!is_null($this->method)) { // if a method is set then use that one
            if (is_string($this->method) && ('swift' == $this->method)) {
                return $this->_swiftMail($to, is_string($from) ? $this->from[$from] : $from, $subject, $message, [], $html);
            } else {
                return call_user_func($this->method, $to, is_string($from) ? $this->from[$from] : $from, $subject, $message, [], $headerExtra, $html);
            }
        } // if not use default
        return $this->_mail($to, is_string($from) ? $this->from[$from] : $from, $subject, $message, [], $headerExtra, $html);
    }