spf2.es.net has no NS records.
NS records for this zone are defined at es.net.
NS records for this zone are defined at es.net.
Question and response
Question
dig spf2.es.net. NS
Answer
The response has no answer records.
Authority
es.net. 600 SOA ns1.es.net. hostmaster.es.net. 2026026240 3600 3600 1209600 600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0