mx.runity.RU has no CNAME records.
Question and response
Question
dig mx.runity.RU. NS
Answer
The response has no answer records.
Authority
runity.RU. 582 SOA cdnsa.nic.RU. noc-dns.nic.RU. 2026022201 14400 3600 2592000 600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0