mail.PFR.RU has no NS records.
NS records for this zone are defined at PFR.RU.
NS records for this zone are defined at PFR.RU.
Question and response
Question
dig mail.PFR.RU. NS
Answer
The response has no answer records.
Authority
pfr.ru. 3600 SOA nsmt.rt.ru. hostmaster.pfr.ru. 1730821232 43200 3600 1814400 3600
Additional
. 0 OPT ; payload 512, xrcode 0, version 0, flags 0