ex.cz.net has no MX records.
Question and response
Question
dig ex.cz.net. MX
Answer
The response has no answer records.
Authority
cz.net. 86400 SOA ns.eunet.cz. hostmaster.cz.net. 2025121100 28800 7200 604800 86400
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0