mail.foxserv.de has no CNAME records.
Question and response
Question
dig mail.foxserv.de. NS
Answer
The response has no answer records.
Authority
foxserv.de. 1485 SOA h2969901.stratoserver.net. alp.patrick-altmann.de. 2026020401 10800 3600 1209600 10800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0