temp.stadtwerke-soest.net has no MX records.
Question and response
Question
dig temp.stadtwerke-soest.net. MX
Answer
The response has no answer records.
Authority
stadtwerke-soest.net. 600 SOA ns01.stadtwerke-soest.net. administrator.stadtwerke-soest.de. 1539792549 10800 3600 604800 38400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0