mail.3bb.co.th has no MX records.
Question and response
Question
dig mail.3bb.co.th. MX
Answer
The response has no answer records.
Authority
3bb.co.th. 300 SOA ns1.3bb.co.th. hostmaster.3bb.co.th. 2026021801 10800 3600 604800 300
Additional
. 0 OPT ; payload 1220, xrcode 0, version 0, flags 0