smtp5.quantum.ru has no CNAME records.
Question and response
Question
dig smtp5.quantum.ru. NS
Answer
The response has no answer records.
Authority
quantum.ru. 2776 SOA ns.quantum.ru. regadmin.quantum.ru. 20240001 28800 7200 604800 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0