hk has no MX records.
Question and response
Question
dig hk. MX
Answer
The response has no answer records.
Authority
hk. 900 SOA ns3.hkirc.net.hk. hostmaster.hkirc.net.hk. 2074894997 1800 900 1209600 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0