ns1.skymail.net.br has no MX records.
Question and response
Question
dig ns1.skymail.net.br. MX
Answer
The response has no answer records.
Authority
skymail.net.br. 2560 SOA ns3.skymail.net.br. hostmaster.skymail.net.br. 1719876728 16384 2048 1048576 2560
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0