_acme-challenge.dbk.dk has no MX records.
Question and response
Question
dig dbk.dk.kinstavalidation.app. MX
Answer
The response has no answer records.
Authority
kinstavalidation.app. 1800 SOA elliott.ns.cloudflare.com. dns.cloudflare.com. 2397523776 10000 2400 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0