ns3.mail.in.th has no CNAME records.
Question and response
Question
dig ns3.mail.in.th. NS
Answer
The response has no answer records.
Authority
mail.in.th. 3600 SOA ns.mail.in.th. hostmaster\.mail.in.th. 2026022719 86400 3600 604800 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0