srvmail6.embratel.com.br has no NS records.
NS records for this zone are defined at embratel.com.br.
NS records for this zone are defined at embratel.com.br.
Question and response
Question
dig srvmail6.embratel.com.br. NS
Answer
The response has no answer records.
Authority
embratel.com.br. 86400 SOA ns.embratel.net.br. admin.embratel.net.br. 2026031901 3600 900 604800 86400
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0