mx.casjay.casa has no CNAME records.
Question and response
Question
dig mx.casjay.casa. NS
Answer
The response has no answer records.
Authority
casjay.casa. 10036 SOA dns.casjay.casa. dns-admin.casjay.casa. 2026010336 10800 3600 1209600 38400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0