mx.email.com.br has no NS records.
NS records for this zone are defined at email.com.br.
NS records for this zone are defined at email.com.br.
Question and response
Question
dig mx.email.com.br. NS
Answer
The response has no answer records.
Authority
email.com.br. 60 SOA ns1.penso.com.br. hostmaster.penso.com.br.email.com.br. 2026021301 7200 3600 1209600 1200
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0