sender20.mail.selcloud.ru has no NS records.
NS records for this zone are defined at mail.selcloud.ru.
NS records for this zone are defined at mail.selcloud.ru.
Question and response
Question
dig sender20.mail.selcloud.ru. NS
Answer
The response has no answer records.
Authority
mail.selcloud.ru. 60 SOA a.ns.selectel.ru. support.selectel.ru. 2026022003 10800 3600 604800 60
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0