ns3.ddnss.de has no MX records.
Question and response
Question
dig ns3.ddnss.de. MX
Answer
The response has no answer records.
Authority
ddnss.de. 60 SOA ns1.ddnss.de. postmaster.megacomputing.de. 2061279298 3600 7200 604800 1800
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0