mx03.fischl-online.de has no MX records.
Question and response
Question
dig mx03.fischl-online.de. MX
Answer
The response has no answer records.
Authority
fischl-online.de. 60 SOA ns03.fischl.online. root.fischl-online.de. 1770431075 28800 7200 2419200 60
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0