mail.1app.com.br has no NS records.
NS records for this zone are defined at 1app.com.br.
NS records for this zone are defined at 1app.com.br.
Question and response
Question
dig mail.1app.com.br. NS
Answer
The response has no answer records.
Authority
1app.com.br. 1800 SOA ns1.digitalocean.com. hostmaster.1app.com.br. 1772030510 10800 3600 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0