mx01.nuva.net.br has no MX records.
Question and response
Question
dig mx01.nuva.net.br. MX
Answer
The response has no answer records.
Authority
nuva.net.br. 1800 SOA ns1.udns.com.br. contato.tmsoft.com.br. 2020081500 10800 900 604800 86400
Additional
. 0 OPT [{Extended_DNS_Error: PROHIBITED}] ; payload 1232, xrcode 0, version 0, flags 0