ns2.sontheimer.eu has no MX records.
Question and response
Question
dig ns2.sontheimer.eu. MX
Answer
The response has no answer records.
Authority
sontheimer.eu. 10800 SOA ns1.sontheimer.de. postmaster.sontheimer.de. 2018082000 43200 180 1209600 10800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0