mailserver.itconnection.se has no CNAME records.
Question and response
Question
dig mailserver.itconnection.se. NS
Answer
The response has no answer records.
Authority
itconnection.se. 428 SOA dns1.itconnection.se. registry.itconnection.se. 1564548822 3600 1200 1209600 7200
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0