mx2.jpberlin.de has no CNAME records.
Question and response
Question
dig mx2.jpberlin.de. NS
Answer
The response has no answer records.
Authority
jpberlin.de. 1449 SOA ns.jpberlin.de. root.jpberlin.de. 2014830892 14400 1800 604800 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0