如何在Codeigniter中使用GMail SMTP获取已读回执？

$this->load->library('email');

$config['protocol'] = 'smtp';
$config['smtp_host'] = 'smtp.gmail.com';
$config['smtp_port'] = '587';
$config['smtp_user'] = 'your_email@gmail.com';
$config['smtp_pass'] = 'your_password';
$config['smtp_crypto'] = 'tls';
$config['mailtype'] = 'html';
$config['charset'] = 'utf-8';
$config['newline'] = "\r\n";

public function send_email_with_read_receipt() {
    $this->load->library('email');
    
    $this->email->from('your_email@gmail.com', 'Your Name');
    $this->email->to('recipient@example.com');
    $this->email->subject('Test Email with Read Receipt');
    $this->email->message('This is a test email with read receipt.');

    // 添加已读回执标记
    $this->email->set_header('Disposition-Notification-To', 'your_email@gmail.com');

    if ($this->email->send()) {
        echo 'Email sent successfully.';
    } else {
        echo 'Email sending failed.';
    }
}

$this->send_email_with_read_receipt();