jixiuf@jf ~ $ telnet mx0.qq.com 25
Trying 58.251.149.190...
Connected to mx0.qq.com.
Escape character is '^]'.
ehlo 10.2.0.2
8
（我的IP）
220 ********************************
250 newmx33.qq.com
mail from:<jixiuf@gmail.com>
250 Ok
rcpt to:<jixiuf@qq.com>
250 Ok
data
354 End data with <CR><LF>.<CR><LF>
from:jixiuf@gmail.combutasaserversoicansendmailwithoutpasswdandusername
subject:maoChongServerSendMail
test!!!
.
250 Ok: queued as
quit
221 Bye
Connection closed by foreign host.
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jixiuf@jf ~ $ nslookup
> set type=mx
（设置查询的类型为mx，即邮件）
> qq.com
（查询qq.com 内部了采用的邮件服务器）
Server: 127.0.0.1
Address: 127.0.0.1#53
Non-authoritative answer:
qq.com mail exchanger = 10 mx0.qq.com.
Authoritative answers can be found from:
qq.com nameserver = dns1.imok.net.
qq.com nameserver = dns2.imok.net.
qq.com nameserver = dns3.imok.net.
//这是查询出的结果（也就是最上面telnet 的地址，注意这里的地址不在是qq官网上公布给大家的smtp.qq.com ，这个地址是需要密码和用户名的，下面的邮件服务器却不需要）
mx0.qq.com internet address = 58.251.149.190
mx0.qq.com internet address = 58.251.149.191
mx0.qq.com internet address = 58.251.149.192
mx0.qq.com internet address = 58.251.149.193
mx0.qq.com internet address = 58.251.149.194
mx0.qq.com internet address = 58.251.149.195
mx0.qq.com internet address = 58.251.149.196
mx0.qq.com internet address = 58.251.149.197
mx0.qq.com internet address = 58.251.149.187
mx0.qq.com internet address = 58.251.149.188
mx0.qq.com internet address = 58.251.149.189
dns2.imok.net internet address = 61.152.100.5
dns3.imok.net internet address = 218.30.72.181
dns1.imok.net internet address = 219.133.40.202
>