ns4.m-online.net has no MX records.
Question and response
Question
dig ns4.m-online.net. MX
Answer
The response has no answer records.
Authority
m-online.net. 1800 SOA ns1.m-online.net. hostmaster.m-net.de. 2026022002 14400 1800 1209600 1800
Additional
. 0 OPT ; payload 1220, xrcode 0, version 0, flags 0