ns4.cray.com.br has no MX records.
Question and response
Question
dig ns4.cray.com.br. MX
Answer
The response has no answer records.
Authority
cray.com.br. 86400 SOA ns3.cray.com.br. rodrigo.mundoopen.com.br. 2026011400 43200 7200 2419200 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0