c10221.hkn.net has no MX records.
Question and response
Question
dig c10221.hkn.net. MX
Answer
The response has no answer records.
Authority
hkn.net. 300 SOA neos.hkn.de. hostmaster.hkn.de. 1772112300 28800 7200 604800 300
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0