_spf.sapo.pt has no NS records.
NS records for this zone are defined at sapo.pt.
NS records for this zone are defined at sapo.pt.
Question and response
Question
dig _spf.sapo.pt. NS
Answer
The response has no answer records.
Authority
sapo.pt. 3600 SOA ns.sapo.pt. root.sapo.pt. 1772714151 3600 7200 2419200 300
Additional
The response has no additional records.