mail.computex.net.br has no CNAME records.
Question and response
Question
dig mail.computex.net.br. NS
Answer
The response has no answer records.
Authority
computex.net.br. 247 SOA ns1.computex.net.br. hostmaster.computex.net.br. 2025063005 14400 7200 2419200 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0