มีปัญหาเรื่อง Codeigniter library Email ที่ส่งออกโดยใช้ gmail ครับ

$config = array(
                'protocol' => 'smtp',
                'smtp_host' => 'smtp.gmail.com',
                'smtp_port' => 465,
                'smtp_timeout' => '5',
                'smtp_user' => '[email protected]',
                'smtp_pass' => 'xxxxx', //เป็นPassword ของ Email
                'mailtype'  => 'html', 
                'charset'   => 'iso-8859-1'
                );
                
                $this->load->library("email",$config);
                $this->load->model("model_users");
                
                $this->email->from("[email protected]","keng_kg");
                $this->email->to($this->input->post("email"));
                $this->email->subject("Confirm your account.");
                
                $message = "<p>Thank you for signing up!<p>";
                $message .= "<p><a href='".base_url()."main/register_user/$key'>Click here</a>
                to confirm your account</p>";
                
                $this->email->message($message);
                if($this->model_users->add_temp_user($key)){
                    if($this->email->send()){
                    echo "The email has been sent!";
                    }else echo "Could not send the email.";
                          echo $this->email->print_debugger();