mx1.stefanux.net has no CNAME records.
Question and response
Question
dig mx1.stefanux.net. NS
Answer
The response has no answer records.
Authority
stefanux.net. 3600 SOA ns.inwx.de. hostmaster.inwx.de. 2025071701 10800 3600 604800 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0