Email 关于SMTP服务器有效性中的SSL协议

上个月，我成功地用这段代码通过PHP发送了一封邮件

if($this->form_validation->run()){
        #generate a random key
        $key = md5(uniqid());
        $this->load->model('model_users');

require_once "swift/lib/swift_required.php";

        $transport = Swift_SmtpTransport::newInstance('smtp.gmail.com', 465, 'ssl')
            ->setUsername('xxxxx@gmail.com')
            ->setPassword('xxxxx');
        // Create the Mailer using your created Transport
                $mailer = Swift_Mailer::newInstance($transport);
                $messagebody = "<p>Thank you for signing up!</p>";
                $messagebody .="<form action= '".base_url()."main/register_user/$key' method='post'> 
                    <input type='submit' value='Activate my Account'> </form> ";

    //  <p><a href='".base_url()."main/register_user/$key'>Click Here</a>  to confirm your account.
        // Create a message
                $message = Swift_Message::newInstance('CBS Account Activation Message')
                  ->setFrom(array('xxxxx@gmail.com' => 'CBS Group'))
                  ->setContentType("text/html")
                  ->setTo(array($this->input->post('email') => $this->input->post('email')))
                  ->setBody($messagebody)
                  ->setMaxLineLength(100)
                 ;
        // Send the message
                $result = $mailer->send($message);

        //send and email to user
                    if($this->model_users->add_temp_user($key)){
                    if($result){
                        echo "The email has been sent!";
                        $this->load->view('signup_success');
                    }
                    else{

                        // Failure Message
                        echo "Could not send mail";
                    }
                }else
                echo "Problem adding to database";


                    #add them to the temp_user db
                }

如果我在另一个系统中使用相同的代码，它将成功运行并将邮件发送到特定的邮件id

我也没有更改代码

我如何解决这个问题

Fatal error: Uncaught exception 'Swift_TransportException' with message 'Connection could not be established with host smtp.gmail.com [ #0]' in C:\xampp\htdocs\code\application\controllers\swift\lib\classes\Swift\Transport\StreamBuffer.php:266 Stack trace: #0 C:\xampp\htdocs\code\application\controllers\swift\lib\classes\Swift\Transport\StreamBuffer.php(64): Swift_Transport_StreamBuffer->_establishSocketConnection() #1 C:\xampp\htdocs\code\application\controllers\swift\lib\classes\Swift\Transport\AbstractSmtpTransport.php(115): Swift_Transport_StreamBuffer->initialize(Array) #2 C:\xampp\htdocs\code\application\controllers\swift\lib\classes\Swift\Mailer.php(80): Swift_Transport_AbstractSmtpTransport->start() #3 C:\xampp\htdocs\code\application\controllers\main.php(370): Swift_Mailer->send(Object(Swift_Message)) #4 [internal function]: Main->forgot_validation() #5 C:\xampp\htdocs\code\system\core\CodeIgniter.php(359): call_user_func_array(Array, Array) #6 C:\xampp\htdocs\code\index.php(202): require_once('C:\\xampp\\htdocs. in C:\xampp\htdocs\code\application\controllers\swift\lib\classes\Swift\Transport\StreamBuffer.php on line 266