mail.builder.ru.eserver.net has no NS records.
NS records for this zone are defined at ru.eserver.net.
NS records for this zone are defined at ru.eserver.net.
Question and response
Question
dig mail.builder.ru.eserver.net. NS
Answer
The response has no answer records.
Authority
builder.ru.eserver.net. 10800 SOA ns4.ru.eserver.net. info.eserver.ru. 2023010901 3600 3600 604800 10800
Additional
. 0 OPT ; payload 1680, xrcode 0, version 0, flags 0