mx-ctdodo.gpool.oss-core.net has no CNAME records.
Question and response
Question
dig mx-ctdodo.gpool.oss-core.net. NS
Answer
The response has no answer records.
Authority
gpool.oss-core.net. 500 SOA sydcoregtm01.gpool.oss-core.net. hostmaster.sydcoregtm01.gpool.oss-core.net. 2025031302 10800 3600 604800 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0