尝试使用Swift mailer，gmail smtp，php发送邮件

这是我的代码：

<?php
require_once 'Swift/lib/swift_required.php';

$transport = Swift_SmtpTransport::newInstance('smtp.gmail.com', 465)
  ->setUsername('me@ff.com')
  ->setPassword('pass');

$mailer = Swift_Mailer::newInstance($transport);
$message = Swift_Message::newInstance('Wonderful Subject')
  ->setFrom(array('me@ff.com' => 'MY NAME'))
  ->setTo(array('you@ss.com' => 'YOU'))
  ->setBody('This is the text of the mail send by Swift using SMTP transport.');
//$attachment = Swift_Attachment::newInstance(file_get_contents('path/logo.png'), 'logo.png');  
//$message->attach($attachment);
$numSent = $mailer->send($message);
printf("Sent %d messages\n", $numSent);
?>

AFter 运行出现此错误...

致命错误：未捕获的异常“Swift_TransportException”，消息“预期响应代码 220 但收到代码”“，消息”“在 /home/sitenyou/public_html/Swift/lib/classes/Swift/Transport/AbstractSmtpTransport 中显示消息”“.php：406

Stack trace: 
#0 /home/sitenyou/public_html/Swift/lib/classes/Swift/Transport/AbstractSmtpTransport.php(299): Swift_Transport_AbstractSmtpTransport->_assertResponseCode('', Array) 
#1 /home/sitenyou/public_html/Swift/lib/classes/Swift/Transport/AbstractSmtpTransport.php(107): Swift_Transport_AbstractSmtpTransport->_readGreeting() 
#2 /home/sitenyou/public_html/Swift/lib/classes/Swift/Mailer.php(74): Swift_Transport_AbstractSmtpTransport->start() 
#3 /home/sitenyou/public_html/sgmail.php(16): Swift_Mailer->send(Object(Swift_Message)) 
#4 {main} thrown in /home/sitenyou/public_html/Swift/lib/classes/Swift/Transport/AbstractSmtpTransport.php on line 406