mx.casjay.work has no CNAME records.
Question and response
Question
dig mx.casjay.work. NS
Answer
The response has no answer records.
Authority
casjay.work. 5664 SOA dns.casjay.work. dns-admin.casjay.work. 2026010366 10800 3600 1209600 38400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0