mx.glasoperator.nl has no CNAME records.
Question and response
Question
dig mx.glasoperator.nl. NS
Answer
The response has no answer records.
Authority
glasoperator.nl. 1749 SOA ns1.versatel.net. hostmaster.versatel.net. 2025111401 10800 3600 604800 7200
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0