attachment is not sent in email in CodeIgniter

Question

when I used this code to send mail in CodeIgniter mail is sent successfully but the attachment is not sent with the email.

$this->email->clear(TRUE); 
    $config = array(
            'protocol' => 'mail',
            'smtp_host' => 'mail.xxxx.in',
            'smtp_port' => 26,
            'smtp_timeout' => 30,
            'smtp_user' => 'example.in',
            'smtp_pass' => 'xxxxx',
            'mailtype' => 'html',
            'mailpatd' => '/usr/sbin/sendmail',
            'charset'  => 'iso-8859-1',
            'priority' =>1
        );
    $this->load->helper('url');
    $this->load->library('email');
    $this->email->initialize($config);
    $this->email->set_newline("\r\n");
    $this->email->from(SITE_SUPPORT_MAIL, 'GD-Associates');
    $this->email->to($mailto);
    $this->email->subject($mailsubject);
    $this->email->message($mailbody);

    if($file_path!='')
    $this->email->attach($file_path);
    $this->email->send();