mx1.smtpenvio.com.br has no NS records.
NS records for this zone are defined at smtpenvio.com.br.
NS records for this zone are defined at smtpenvio.com.br.
Question and response
Question
dig mx1.smtpenvio.com.br. NS
Answer
The response has no answer records.
Authority
smtpenvio.com.br. 300 SOA ns1.p68.dns.oraclecloud.net. hostmaster.smtpenvio.com.br. 11 3600 600 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0