mail.tmknet.com.br has no MX records.
Question and response
Question
dig mail.tmknet.com.br. MX
Answer
The response has no answer records.
Authority
tmknet.com.br. 3600 SOA ns1.tmknet.com.br. root.tmknet.com.br. 2505150944 10800 3600 7200 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0