sta.inet.co.th has no MX records.
Question and response
Question
dig sta.inet.co.th. MX
Answer
The response has no answer records.
Authority
sta.inet.co.th. 300 SOA ns01.inet.co.th. hostmaster.inet.co.th. 2117345615 21600 3600 2419200 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0