mail.GTCONLINE.RU has no NS records.
NS records for this zone are defined at GTCONLINE.RU.
NS records for this zone are defined at GTCONLINE.RU.
Question and response
Question
dig mail.GTCONLINE.RU. NS
Answer
The response has no answer records.
Authority
gtconline.ru. 3600 SOA ns1.gtconline.ru. root.ns1.gtconline.ru. 2018101502 10800 3600 1209600 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0