bg3.exmail.qq.com has no NS records.
NS records for this zone are defined at exmail.qq.com.
NS records for this zone are defined at exmail.qq.com.
Question and response
Question
dig bg3.exmail.qq.com. NS
Answer
The response has no answer records.
Authority
exmail.qq.com. 180 SOA ns-tel1.qq.com. webmaster.qq.com. 1768811932 300 600 86400 180
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0