smtpout.3bbmail.com has no MX records.
Question and response
Question
dig smtpout.3bbmail.com. MX
Answer
The response has no answer records.
Authority
3bbmail.com. 120 SOA ns1.3bb.co.th. hostmaster.3bbmail.com. 2026012902 10800 3600 604800 120
Additional
. 0 OPT ; payload 1220, xrcode 0, version 0, flags 0