spf2.knipp.de has no MX records.
Question and response
Question
dig spf2.knipp.de. MX
Answer
The response has no answer records.
Authority
knipp.de. 900 SOA ns7.knipp.de. dnsmaster.knipp.de. 2026022085 10800 3600 604800 900
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0