ns2.webcerta.com.br has no MX records.
Question and response
Question
dig ns2.webcerta.com.br. MX
Answer
The response has no answer records.
Authority
ns2.webcerta.com.br. 5788 SOA ns1.w3connect.com.br. felipe.deieno.com.br. 2017121501 3600 7200 1209600 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0