mx1.high5.nl has no CNAME records.
Question and response
Question
dig mx1.high5.nl. NS
Answer
The response has no answer records.
Authority
high5.nl. 934 SOA ns1.high5.nl. hostmaster.high5.nl. 2026022200 14400 3600 1209600 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0