mailap01.hkbn.com.hk has no MX records.
Question and response
Question
dig mailap01.hkbn.com.hk. MX
Answer
The response has no answer records.
Authority
hkbn.com.hk. 3600 SOA ns1.hkbn.net. sysadm.ns1.hkbn.net. 2026030402 3600 1800 604800 3600
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0