mx03.mh.bkk1.cloud.z.com has no CNAME records.
Question and response
Question
dig mx03.mh.bkk1.cloud.z.com. NS
Answer
The response has no answer records.
Authority
mh.bkk1.cloud.z.com. 1279 SOA ns-a1.cloud.z.com. postmaster.example.com. 1510309953 3600 600 86400 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0