sysdb.pacific.net.th has no MX records.
Question and response
Question
dig sysdb.pacific.net.th. MX
Answer
The response has no answer records.
Authority
pacific.net.th. 300 SOA ns1.pacific.net.th. postmaster.ns1.pacific.net.th. 2026022000 21600 1800 1209600 300
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0