ns5o.ctihk.com has no MX records.
Question and response
Question
dig ns5o.ctihk.com. MX
Answer
The response has no answer records.
Authority
ctihk.com. 3600 SOA ns1o.ctihk.com. sysadm.ns1o.ctihk.com. 2026012801 3600 3600 604800 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0