印第安纳波利斯500:请nslookup高手进来，重谢

C:\>nslookup
*** Can't find server name for address 192.168.3.19: Non-existent domain
*** Default servers are not available
Default Server: UnKnown
Address: 192.168.3.19

> set type=mx
> 163.com
Server: UnKnown
Address: 192.168.3.19

Non-authoritative answer:
163.com MX preference = 50, mail exchanger = mx.mail.163.split.netease.com

mx.mail.163.split.netease.com internet address = 220.181.12.53
mx.mail.163.split.netease.com internet address = 220.181.12.54
mx.mail.163.split.netease.com internet address = 220.181.12.55
mx.mail.163.split.netease.com internet address = 220.181.12.56
mx.mail.163.split.netease.com internet address = 220.181.12.57
mx.mail.163.split.netease.com internet address = 220.181.12.58
mx.mail.163.split.netease.com internet address = 220.181.12.51
mx.mail.163.split.netease.com internet address = 220.181.12.52
> szdsib.com
Server: UnKnown
Address: 192.168.3.19

szdsib.com
primary name server = (root)
responsible mail addr = hostmaster.nameserver
serial = 166
refresh = 28800 (8 hours)
retry = 7200 (2 hours)
expire = 604800 (7 days)
default TTL = 5 (5 secs)
>

如上所示，163.com能够正常检测出来其对应的邮件服务器地址，但是szdsib.com却显示如上信息，请高手帮我解读和分析一下，这样的信息到底表明了什么问题？！