mx1.volgograd.ertelecom.ru has no NS records.
NS records for this zone are defined at volgograd.ertelecom.ru.
NS records for this zone are defined at volgograd.ertelecom.ru.
Question and response
Question
dig mx1.volgograd.ertelecom.ru. NS
Answer
The response has no answer records.
Authority
volgograd.ertelecom.ru. 3600 SOA ns8.ertelecom.ru. noc.ertelecom.ru. 2026020603 28800 7200 604800 86400
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0