mailserver.aowin.com.br has no CNAME records.
Question and response
Question
dig mailserver.aowin.com.br. NS
Answer
The response has no answer records.
Authority
aowin.com.br. 3568 SOA ns1.gegnet.net.br. suporte.gegnet.net.br. 2025021081 3600 3600 86400 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0