mailserver.gegnet.net.br has no CNAME records.
Question and response
Question
dig mailserver.gegnet.net.br. NS
Answer
The response has no answer records.
Authority
gegnet.net.br. 2574 SOA ns1.gegnet.net.br. suporte.gegnet.net.br. 2024041104 3600 3600 86400 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0