mailman.webbycloud.com.br has no NS records.
NS records for this zone are defined at webbycloud.com.br.
NS records for this zone are defined at webbycloud.com.br.
Question and response
Question
dig mailman.webbycloud.com.br. NS
Answer
mailman.webbycloud.com.br. 86400 NS ns1.webbycloud.com.br.
mailman.webbycloud.com.br. 86400 NS ns2.webbycloud.com.br.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0