ns.s2p.de has no MX records.
Question and response
Question
dig ns.s2p.de. MX
Answer
The response has no answer records.
Authority
s2p.de. 1800 SOA adenin.s2p.de. hostmaster.s2p.de. 1914 86400 7200 2419200 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0