spf.sendinblue.com has no NS records.
NS records for this zone are defined at sendinblue.com.
NS records for this zone are defined at sendinblue.com.
Question and response
Question
dig spf.sendinblue.com. NS
Answer
The response has no answer records.
Authority
sendinblue.com. 1800 SOA josh.ns.cloudflare.com. dns.cloudflare.com. 2397514272 10000 2400 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0