smtp01.ntt.com.sg has no NS records.
NS records for this zone are defined at ntt.com.sg.
NS records for this zone are defined at ntt.com.sg.
Question and response
Question
dig smtp01.ntt.com.sg. NS
Answer
The response has no answer records.
Authority
ntt.com.sg. 300 SOA ns1-09.azure-dns.com. dnsadmin.ntts-idc.net.sg. 2024091200 14400 7200 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0