mail-tk.wdservice.center has no MX records.
Question and response
Question
dig mail-tk.wdservice.center. MX
Answer
The response has no answer records.
Authority
wdservice.center. 300 SOA dns1rz.world-direct.at. administrator.world-direct.at. 2015120101 10800 1350 2419200 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0