mail.cloud4box.ru has no CNAME records.
Question and response
Question
dig mail.cloud4box.ru. NS
Answer
The response has no answer records.
Authority
cloud4box.ru. 2569 SOA ns1.contell.ru. tech.contell.ru. 2021140737 10800 3600 604800 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0