mail.bluem.nl has no CNAME records.
Question and response
Question
dig mail.bluem.nl. NS
Answer
The response has no answer records.
Authority
bluem.nl. 1998 SOA dns0.domeinbalie.nl. service.domeinbalie.nl. 2026030501 10800 3600 604800 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0