ns4.domain24.de has no MX records.
Question and response
Question
dig ns4.domain24.de. MX
Answer
The response has no answer records.
Authority
domain24.de. 300 SOA ns1.domain24.com. hostmaster.domain24.com. 2026021600 28800 7200 604800 300
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0