mx.baitong-valve.com has no CNAME records.
Question and response
Question
dig mx.baitong-valve.com. NS
Answer
The response has no answer records.
Authority
baitong-valve.com. 3453 SOA dns.baitong-valve.com. hostmaster.baitong-valve.com. 1144132982 43200 3600 604800 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0