_cf-custom-hostname.postmaster.heysender.com has no NS records.
NS records for this zone are defined at heysender.com.
NS records for this zone are defined at heysender.com.
Question and response
Question
dig _cf-custom-hostname.postmaster.heysender.com. NS
Answer
The response has no answer records.
Authority
heysender.com. 300 SOA ns1.curanet.dk. hostmaster.curanet.dk. 2026030201 14400 3600 1209600 300
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0