ns5.udns.com.br has no MX records.
Question and response
Question
dig ns5.udns.com.br. MX
Answer
The response has no answer records.
Authority
udns.com.br. 3600 SOA ns1.udns.com.br. noc.udns.com.br. 2025091701 10800 900 604800 86400
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0