ns2.rcatelecom.com.br has no MX records.
Question and response
Question
dig ns2.rcatelecom.com.br. MX
Answer
The response has no answer records.
Authority
rcatelecom.com.br. 900 SOA ns1.rcatelecom.com.br. carloseduardo.layer7tecnologia.com.br. 2015050643 1800 900 604800 900
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0