bkk1.cloud.z.com has no MX records.
Question and response
Question
dig bkk1.cloud.z.com. MX
Answer
The response has no answer records.
Authority
bkk1.cloud.z.com. 3600 SOA ns-a1.zc-dns.com. postmaster.example.com. 1756971324 3600 600 86400 3600
Additional
. 0 OPT ; payload 2800, xrcode 0, version 0, flags 0