ns21.netuse.de has no MX records.
Question and response
Question
dig ns21.netuse.de. MX
Answer
The response has no answer records.
Authority
netuse.de. 3600 SOA ns21.netuse.de. hostmaster.netuse.de. 2026030205 3600 1200 3600000 3600
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0