mx.mail.postal.copyleft.no has no CNAME records.
Question and response
Question
dig mx.mail.postal.copyleft.no. NS
Answer
The response has no answer records.
Authority
copyleft.no. 208 SOA dns10.copyleft.no. hostmaster.copyleft.no. 3000010675 28800 7200 604800 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0