mx128.e.outbound.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 mx128.e.outbound.createsend.com. NS
Answer
The response has no answer records.
Authority
createsend.com. 180 SOA ns10.digicertdns.com. dns.digicertdns.com. 2009010162 43200 3600 1209600 180
Additional
. 0 OPT ; payload 1280, xrcode 0, version 0, flags 0