Network Misc

http://segmentfault.com/a/1190000002452103

好了，现在我们已经大致知道邮件是如何发送、接收的了，那么巨人是如何封锁掉Gmail的？难道是DNS劫持或者是DNS污染？我们先查看一下Gmail邮件发送服务器stmp.gmail.com的域名记录，如下：

$ nslookup smtp.gmail.com
Server:        192.168.1.1
Address:    192.168.1.1#53

Non-authoritative answer:
smtp.gmail.com    canonical name = gmail-smtp-msa.l.google.com.
Name:    gmail-smtp-msa.l.google.com
Address: 74.125.203.108
Name:    gmail-smtp-msa.l.google.com
Address: 74.125.203.109

地址没问题，看来不是DNS的问题了，那么应该就是直接封了Gmail的SMTP、POP3、IMAP服务器的IP了，证据如下(以POP3为例)：

$ ping pop.gmail.com
PING gmail-pop.l.google.com (74.125.31.109): 56 data bytes
Request timeout for icmp_seq 0
Request timeout for icmp_seq 1
Request timeout for icmp_seq 2
^C
--- gmail-pop.l.google.com ping statistics ---
4 packets transmitted, 0 packets received, 100.0% packet loss