mail.stroiprint.ru has no CNAME records.
Question and response
Question
dig mail.stroiprint.ru. NS
Answer
The response has no answer records.
Authority
stroiprint.ru. 3492 SOA firstvds.ru. tech.firstvds.ru. 2019020610 10800 3600 604800 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0