kl.dynamdns.de has no MX records.
Question and response
Question
dig kl.dynamdns.de. MX
Answer
The response has no answer records.
Authority
dynamdns.de. 60 SOA ns.owe.de. hostmaster.owe.de. 5127 10800 3600 604800 86400
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0