_spf.rdstation.com.br has no NS records.
NS records for this zone are defined at rdstation.com.br.
NS records for this zone are defined at rdstation.com.br.
Question and response
Question
dig _spf.rdstation.com.br. NS
Answer
The response has no answer records.
Authority
rdstation.com.br. 900 SOA ns-132.awsdns-16.com. awsdns-hostmaster.amazon.com. 1 7200 900 1209600 86400
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0