mail.EGSTELECOM.RU has no CNAME records.
Question and response
Question
dig mail.EGSTELECOM.RU. NS
Answer
The response has no answer records.
Authority
egstelecom.ru. 2494 SOA ns.egstelecom.ru. root.ns.egstelecom.ru. 2022072501 3600 900 1814400 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0