mx02.mail.alibaba.com has no NS records.
NS records for this zone are defined at alibaba.com.
NS records for this zone are defined at alibaba.com.
Question and response
Question
dig mx02.mail.alibaba.com. NS
Answer
The response has no answer records.
Authority
alibaba.com. 600 SOA ns1.alibabadns.com. hostmaster.alibabadns.com. 2018051019 3600 1200 86400 360
Additional
. 0 OPT ; payload 1280, xrcode 0, version 0, flags 0