mx1.hkbn.com.hk has no CNAME records.
Question and response
Question
dig mx1.hkbn.com.hk. NS
Answer
The response has no answer records.
Authority
hkbn.com.hk. 548 SOA ns1.hkbn.net. sysadm.ns1.hkbn.net. 2026030402 3600 1800 604800 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0