spf.protection.outlook.de has no MX records.
Question and response
Question
dig spf.protection.outlook.de. MX
Answer
The response has no answer records.
Authority
protection.outlook.de. 300 SOA ns1-36.azure-dns.com. hostmaster.o365filtering.com. 2024031911 10800 3600 604800 300
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0