mailopp.opportunity.com.br has no NS records.
NS records for this zone are defined at opportunity.com.br.
NS records for this zone are defined at opportunity.com.br.
Question and response
Question
dig mailopp.opportunity.com.br. NS
Answer
The response has no answer records.
Authority
opportunity.com.br. 300 SOA ns-cloud-c1.googledomains.com. cloud-dns-hostmaster.google.com. 5339 21600 3600 259200 300
Additional
. 0 OPT ; payload 512, xrcode 0, version 0, flags 0