spf.mx-rec.de has no CNAME records.
Question and response
Question
dig spf.mx-rec.de. NS
Answer
The response has no answer records.
Authority
mx-rec.de. 2093 SOA hydrogen.ns.hetzner.com. dns.hetzner.com. 2026021900 86400 10800 3600000 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0