dynamic.adsl.gvt.net.br has no MX records.
Question and response
Question
dig dynamic.adsl.gvt.net.br. MX
Answer
The response has no answer records.
Authority
dynamic.adsl.gvt.net.br. 21600 SOA dns1.gvt.net.br. operacao.gvt.net.br. 1497 28800 14400 604800 86400
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0