mail.RUSONYX.RU has no CNAME records.
Question and response
Question
dig mail.RUSONYX.RU. NS
Answer
The response has no answer records.
Authority
rusonyx.ru. 3600 SOA sns1.rsnx.ru. noc.rusonyx.net. 2026011209 7200 3600 1209600 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0