_spf.spnr.de has no CNAME records.
Question and response
Question
dig _spf.spnr.de. NS
Answer
The response has no answer records.
Authority
spnr.de. 55 SOA nox.spnr.de. hostmaster.spnr.de. 12981 14400 3600 1209600 300
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0