public function setDefaultHeader()
    {
        $this->headers[] = "Mime-Version: 1.0";
        $this->headers[] = "Date: " . date("r");
        $this->headers[] = "X-Mailer: PHP/".phpversion();

        if ($this->subject) {
            $this->headers[] = "Subject: " . $this->subject;
        }
    }