_spf.createsend.com has no NS records.
NS records for this zone are defined at createsend.com.
NS records for this zone are defined at createsend.com.
Question and response
Question
dig _spf.createsend.com. NS
Answer
The response has no answer records.
Authority
createsend.com. 180 SOA ns10.digicertdns.com. dns.digicertdns.com. 2009010160 43200 3600 1209600 180
Additional
. 0 OPT ; payload 1280, xrcode 0, version 0, flags 0