mx.mailcloud.com.cn has no CNAME records.
Question and response
Question
dig mx.mailcloud.com.cn. NS
Answer
The response has no answer records.
Authority
mailcloud.com.cn. 116 SOA ns3.dnsv2.com. level3dnsadmin.dnspod.com. 1758182851 3600 180 1209600 180
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0