rmail01.fon.bet has no NS records.
NS records for this zone are defined at fon.bet.
NS records for this zone are defined at fon.bet.
Question and response
Question
dig rmail01.fon.bet. NS
Answer
The response has no answer records.
Authority
fon.bet. 300 SOA ns1.edgedns.ru. support.edgecenter.ru. 1774284127 5400 3600 1209600 300
Additional
. 0 OPT ; payload 1280, xrcode 0, version 0, flags 0