mx.ntnu.no has no CNAME records.
Question and response
Question
dig mx.ntnu.no. NS
Answer
The response has no answer records.
Authority
ntnu.no. 3272 SOA dnsadmin.itea.ntnu.no. hostmaster.ntnu.no. 2026021200 28800 3600 2419200 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0