ns7.alidns.com has no CNAME records.
Question and response
Question
dig ns7.alidns.com. NS
Answer
The response has no answer records.
Authority
alidns.com. 1194 SOA ns3.aliyun.com. hostmaster.alibabadns.com. 2018052320 3600 1200 3600 360
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0