mx01.dgcsystems.net has no CNAME records.
Question and response
Question
dig mx01.dgcsystems.net. NS
Answer
The response has no answer records.
Authority
dgcsystems.net. 459 SOA ns1.dgcsystems.net. registry.dgc.se. 2026012701 3600 600 86400 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0