mx1.docsellent.de has no CNAME records.
Question and response
Question
dig mx1.docsellent.de. NS
Answer
The response has no answer records.
Authority
docsellent.de. 5139 SOA ns013.paragon-cc.de. ddi-pl.atos.net. 2023101815 43200 3600 1209600 10800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0