outgateway.wtthk.com.hk has no MX records.
Question and response
Question
dig outgateway.wtthk.com.hk. MX
Answer
The response has no answer records.
Authority
wtthk.com.hk. 7200 SOA ns1.hkbn.net. sysadm.ns1.hkbn.net. 2026012801 1800 900 86400 7200
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0