ns4.limenet.de has no MX records.
Question and response
Question
dig ns4.limenet.de. MX
Answer
The response has no answer records.
Authority
limenet.de. 7200 SOA ns5.kasserver.com. hostmaster.kasserver.com. 2601071008 28800 7200 1209600 7200
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0