mxmail.netease.com has no NS records.
NS records for this zone are defined at netease.com.
NS records for this zone are defined at netease.com.
Question and response
Question
dig mxmail.netease.com. NS
Answer
The response has no answer records.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0