mailserver.alunoest.com.br has no NS records.
NS records for this zone are defined at alunoest.com.br.
NS records for this zone are defined at alunoest.com.br.
Question and response
Question
dig mailserver.alunoest.com.br. NS
Answer
The response has no answer records.
Authority
alunoest.com.br. 1800 SOA kim.ns.cloudflare.com. dns.cloudflare.com. 2396801106 10000 2400 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0