mailserver3-s2.altcloud.net.br has no CNAME records.
Question and response
Question
dig mailserver3-s2.altcloud.net.br. NS
Answer
The response has no answer records.
Authority
altcloud.net.br. 16 SOA ns1.altcloud.net.br. noc.gegnet.com.br. 2025120301 3600 3600 3600 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0