_spf.correioseguro.com.br has no NS records.
NS records for this zone are defined at correioseguro.com.br.
NS records for this zone are defined at correioseguro.com.br.
Question and response
Question
dig _spf.correioseguro.com.br. NS
Answer
The response has no answer records.
Authority
correioseguro.com.br. 900 SOA ns-937.awsdns-53.net. postmaster.correioseguro.com.br. 1 7200 900 1209600 86400
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0