mail.str01.ru has no NS records.
NS records for this zone are defined at str01.ru.
NS records for this zone are defined at str01.ru.
Question and response
Question
dig mail.str01.ru. NS
Answer
The response has no answer records.
Authority
str01.ru. 1200 SOA ns01.xelent.cloud. support.xelent.cloud. 2026031201 1800 900 604800 1200
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0