smtp.klfree.net has no MX records.
Question and response
Question
dig smtp.klfree.net. MX
Answer
The response has no answer records.
Authority
klfree.net. 14400 SOA ns1.klfree.cz. root.klfree.net. 1771881585 10800 3600 604800 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0