mailman.webbycloud.com.br has no CNAME records.
Question and response
Question
dig mailman.webbycloud.com.br. NS
Answer
The response has no answer records.
Authority
webbycloud.com.br. 3500 SOA a.misconfigured.powerdns.server. hostmaster.webbycloud.com.br. 2025070404 10800 3600 604800 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0