21755729.spf03.hubspotemail.net has no NS records.
NS records for this zone are defined at spf03.hubspotemail.net.
NS records for this zone are defined at spf03.hubspotemail.net.
Question and response
Question
dig 21755729.spf03.hubspotemail.net. NS
Answer
The response has no answer records.
Authority
spf03.hubspotemail.net. 180 SOA ns10.digicertdns.com. dns.digicertdns.com. 2009010107 43200 3600 1209600 180
Additional
. 0 OPT ; payload 1280, xrcode 0, version 0, flags 0