mail.ELSSRV.ru has no CNAME records.
Question and response
Question
dig mail.ELSSRV.ru. NS
Answer
The response has no answer records.
Authority
ELSSRV.ru. 1682 SOA ns1.domenus.ru. support.domenus.ru. 2025121857 3600 300 1209600 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0