mx1.inxmail.de has no CNAME records.
Question and response
Question
dig mx1.inxmail.de. NS
Answer
The response has no answer records.
Authority
inxmail.de. 3454 SOA ns1.dmz.inxmail.de. hostmaster.inxmail.de. 2026021701 3600 1200 604800 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0