Php 由于关联方未正确响应，zend mail失败

我使用php zend mail发送电子邮件。在我进入新的网络环境之前，这些代码运行良好。我使用的php zend邮件代码是：

$mail = new Zend_Mail('UTF-8');
$mail->addTo($toemail, "{".$toname ."}");
$mail->setSubject($subject) ; 
$mail->setFrom($reply_email, 'staff');
$mail->setBodyHTML($msg, 'UTF-8');
try {
    $mail->send();
} catch (Zend_Mail_Protocol_Exception  $e){
    $mailerr = $e->getMessage() ;
    echo  "Send mail fails : ". $mailerr . "<br>" ; 
}

在这里，我们看到我可以ping www.hotmail.com，但我不能ping www.msn.com或我的电子邮件服务器pop域。但是，我可以在浏览器中访问www.hotmail.com和www.msn.com

---

有专家能告诉我zend mail或网络设置有什么问题吗？谢谢

一些流行的网站，如amazon.com、microsoft.com、slashdot.org和其他过去遭受过DoS攻击的网站，可能会在其服务器上禁用ICMP或设置其他网络设置，以阻止接收或响应ping请求。因此，在ping这些域名或其关联的IP地址时，您将收到“请求超时”或“100%数据包丢失”

这是这些网站的正常行为，没有什么办法可以绕过它

C:\Users\Jordan>ping www.hotmail.com

Pinging dispatch.kahuna.glbdns2.microsoft.com [65.55.129.171] with 32 bytes of data:
Reply from 65.55.129.171: bytes=32 time=18ms TTL=246
Reply from 65.55.129.171: bytes=32 time=27ms TTL=246
Reply from 65.55.129.171: bytes=32 time=23ms TTL=246
Reply from 65.55.129.171: bytes=32 time=20ms TTL=246

Ping statistics for 65.55.129.171:
    Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
    Minimum = 18ms, Maximum = 27ms, Average = 22ms


C:\Users\Jordan>
C:\Users\Jordan>ping www.msn.com

Pinging us.co1.cb3.glbdns2.microsoft.com [131.253.13.140] with 32 bytes of data:
Request timed out.
Request timed out.
Request timed out.
Request timed out.

Ping statistics for 131.253.13.140:
    Packets: Sent = 4, Received = 0, Lost = 4 (100% loss),