mx4.fiord.ru has no CNAME records.
Question and response
Question
dig mx4.fiord.ru. NS
Answer
The response has no answer records.
Authority
fiord.ru. 2545 SOA ns1.fiord.ru. noc.fiord.ru. 2026021900 14400 1800 2592000 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0