mx1.servicedomru.ru has no CNAME records.
Question and response
Question
dig mx1.servicedomru.ru. NS
Answer
The response has no answer records.
Authority
servicedomru.ru. 2204 SOA ns8.ertelecom.ru. noc.ertelecom.ru. 2022112801 28800 7200 604800 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0