smtp02.topdns.com has no NS records.
NS records for this zone are defined at topdns.com.
NS records for this zone are defined at topdns.com.
Question and response
Question
dig smtp02.topdns.com. NS
Answer
The response has no answer records.
Authority
topdns.com. 3600 SOA ns-uk.topdns.com. hostmaster.topdns.com. 2026022703 43200 900 1209600 3600
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0