mx-01.winsped.de has no CNAME records.
Question and response
Question
dig mx-01.winsped.de. NS
Answer
The response has no answer records.
Authority
winsped.de. 10800 SOA rz-ns-01.winsped.de. administrator.lis.eu. 2012033270 21600 21600 864000 43200
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0