mail.avency.de has no CNAME records.
Question and response
Question
dig mail.avency.de. NS
Answer
The response has no answer records.
Authority
avency.de. 85 SOA theopolis.avency.de. postmaster.theopolis.avency.de. 2026030545 28800 7200 604800 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0