ns5.name-server-kas.de has no MX records.
Question and response
Question
dig ns5.name-server-kas.de. MX
Answer
The response has no answer records.
Authority
de. 7200 SOA f.nic.de. dns-operations.denic.de. 1771973425 7200 7200 3600000 7200
Additional
. 0 OPT ; payload 1452, xrcode 0, version 0, flags 0