relay20.thaicloudsolutions.com has no MX records.
Question and response
Question
dig relay20.thaicloudsolutions.com. MX
Answer
The response has no answer records.
Authority
thaicloudsolutions.com. 3600 SOA ns-a1.cloud.z.com. postmaster.example.org. 1772787805 3600 600 86400 3600
Additional
. 0 OPT ; payload 2800, xrcode 0, version 0, flags 0