mail.ipzero.com.br has no NS records.
NS records for this zone are defined at ipzero.com.br.
NS records for this zone are defined at ipzero.com.br.
Question and response
Question
dig mail.ipzero.com.br. NS
Answer
The response has no answer records.
Authority
ipzero.com.br. 1800 SOA hera.ns.cloudflare.com. dns.cloudflare.com. 2397934035 10000 2400 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0