mx-slave-01.nimag.net has no CNAME records.
Question and response
Question
dig mx-slave-01.nimag.net. NS
Answer
The response has no answer records.
Authority
nimag.net. 300 SOA ns1.nimag.net. dns-tech.nimag.net. 2026021101 14400 3600 1209600 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0