ip6.code-planet.de has no MX records.
Question and response
Question
dig ip6.code-planet.de. MX
Answer
The response has no answer records.
Authority
code-planet.de. 1800 SOA ns1.smart-weblications.de. hostmaster.smart-weblications.de. 2020051800 10800 7200 604800 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0