mail.TELE-PLUS.RU has no CNAME records.
Question and response
Question
dig mail.TELE-PLUS.RU. NS
Answer
The response has no answer records.
Authority
tele-plus.ru. 4538 SOA ns.tele-plus.ru. admins.tele-plus.ru. 2026100202 28800 7200 1209600 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0