spf.diligent.com has no NS records.
NS records for this zone are defined at diligent.com.
NS records for this zone are defined at diligent.com.
Question and response
Question
dig spf.diligent.com. NS
Answer
The response has no answer records.
Authority
diligent.com. 1800 SOA ns1-07.azure-dns.com. itservices.boardbooks.com. 2020092400 3600 600 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0