mx.kornet.net has no CNAME records.
Question and response
Question
dig mx.kornet.net. NS
Answer
The response has no answer records.
Authority
kornet.net. 10800 SOA ns.kornet.net. domain.ns.kornet.net. 2026010701 43200 3600 604800 43200
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0