_spf.inwx.net has no MX records.
Question and response
Question
dig _spf.inwx.net. MX
Answer
The response has no answer records.
Authority
inwx.net. 3600 SOA ns.inwx.de. hostmaster.inwx.de. 2026022302 10800 3600 604800 3600
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0