mx4.casjay.pro has no CNAME records.
Question and response
Question
dig mx4.casjay.pro. NS
Answer
The response has no answer records.
Authority
casjay.pro. 10525 SOA dns.casjay.pro. dns-admin.casjay.pro. 2026010360 10800 3600 1209600 38400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0