spf.mailcore.net has no NS records.
NS records for this zone are defined at mailcore.net.
NS records for this zone are defined at mailcore.net.
Question and response
Question
dig spf.mailcore.net. NS
Answer
The response has no answer records.
Authority
mailcore.net. 3600 SOA ns21.cloudns.net. postmaster.mailcore.com. 2026022502 7200 1800 1209600 3600
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0