mx.thesecretsofdogtraining.com has no CNAME records.
Question and response
Question
dig mx.thesecretsofdogtraining.com. NS
Answer
The response has no answer records.
Authority
thesecretsofdogtraining.com. 3486 SOA dns.thesecretsofdogtraining.com. hostmaster.thesecretsofdogtraining.com. 1605704310 43200 3600 604800 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0