ip.135.13.user.trestsko.net has no MX records.
Question and response
Question
dig ip.135.13.user.trestsko.net. MX
Answer
The response has no answer records.
Authority
trestsko.net. 2560 SOA ns1.websupport.cz. admin.websupport.cz. 1754116519 7200 2048 1048576 2560
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0