ns1.onitel.com.br has no MX records.
Question and response
Question
dig ns1.onitel.com.br. MX
Answer
The response has no answer records.
Authority
onitel.com.br. 2880 SOA ns1.onitel.com.br. root.onitel.com.br. 20191145 28800 7200 2419200 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0