mail.dwsistemas.net has no MX records.
Question and response
Question
dig mail.dwsistemas.net. MX
Answer
The response has no answer records.
Authority
dwsistemas.net. 3600 SOA dws00.dwsistemas.net. hostmaster.dwsistemas.net. 2017021226 1200 600 86400 3600
Additional
. 0 OPT ; payload 4000, xrcode 0, version 0, flags 0