mx5a.sentia.nl has no CNAME records.
Question and response
Question
dig mx5a.sentia.nl. NS
Answer
The response has no answer records.
Authority
sentia.nl. 2267 SOA dns1.sentia.dk. hostmaster.sentia.dk. 2025060601 10800 3600 604800 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0