public function setAttachment($file = '', $clear = false)
    {
        if (true===$clear) {
            $this->clear('text');
        }
        if (is_array($file)) {
            foreach ($file as $_f) {
                if (file_exists($_f)) {
                    $this->attachment[] = $_f;
                }
            }
        } else {
            if (file_exists($file)) {
                $this->attachment[] = $file;
            }
        }
        return $this;
    }