tot5.tot.co.th has no MX records.
Question and response
Question
dig tot5.tot.co.th. MX
Answer
The response has no answer records.
Authority
tot.co.th. 900 SOA idns1.intranet.tot.co.th. nsmaster.tot.co.th. 1031 10800 3600 2419200 900
Additional
. 0 OPT ; payload 1220, xrcode 0, version 0, flags 0