mail-02.bt.systems has no NS records.
NS records for this zone are defined at bt.systems.
NS records for this zone are defined at bt.systems.
Question and response
Question
dig mail-02.bt.systems. NS
Answer
The response has no answer records.
Authority
bt.systems. 600 SOA ns1.bt.systems. dns.bt.systems. 2025081901 86400 7200 3600000 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0