_spf.netzwerge.de has no MX records.
Question and response
Question
dig _spf.netzwerge.de. MX
Answer
The response has no answer records.
Authority
netzwerge.de. 300 SOA ns1.netzwerge.de. hostmaster.netzwerge.de. 2025021297 28800 7200 2419200 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0