mx.your-storageshare.de has no CNAME records.
Question and response
Question
dig mx.your-storageshare.de. NS
Answer
The response has no answer records.
Authority
your-storageshare.de. 10 SOA ns1.first-ns.de. postmaster.your-storageshare.de. 1772026477 180 60 3600000 10
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0