mail.sovross.ru has no CNAME records.
Question and response
Question
dig mail.sovross.ru. NS
Answer
The response has no answer records.
Authority
sovross.ru. 1962 SOA mail.sovross.ru. tdi.sovross.ru. 2025012218 10800 3600 604800 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0