spf.vsenet.de has no MX records.
Question and response
Question
dig spf.vsenet.de. MX
Answer
The response has no answer records.
Authority
vsenet.de. 3600 SOA ns1.vsenet.net. hostmaster.vsenet.net. 2026012903 86400 10800 604800 3600
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0