mail12.gandi.net has no CNAME records.
Question and response
Question
dig mail12.gandi.net. NS
Answer
The response has no answer records.
Authority
gandi.net. 549 SOA dns0.gandi.net. hostmaster.gandi.net. 2026030501 900 900 1209600 1200
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0