smtp.decks.de has no CNAME records.
Question and response
Question
dig smtp.decks.de. NS
Answer
The response has no answer records.
Authority
decks.de. 3600 SOA ns1.first-ns.de. dns.hetzner.com. 2026021200 14400 1800 604800 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0