mx666.kapper.net has no CNAME records.
Question and response
Question
dig mx666.kapper.net. NS
Answer
The response has no answer records.
Authority
kapper.net. 110 SOA ns1.kapper.net. hostmaster.kapper.net. 2024072578 14400 3600 1814400 900
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0