spf.mcdns.com.br has no MX records.
Question and response
Question
dig spf.mcdns.com.br. MX
Answer
The response has no answer records.
Authority
mcdns.com.br. 3600 SOA pns31.cloudns.net. support.cloudns.net. 2025080101 7200 1800 1209600 3600
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0