mx2.feishu.cn has no CNAME records.
Question and response
Question
dig mx2.feishu.cn. NS
Answer
The response has no answer records.
Authority
feishu.cn. 600 SOA vip3.alidns.com. hostmaster.hichina.com. 2025121107 3600 1200 86400 600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0