smtp.page-educ.fr has no CNAME records.
Question and response
Question
dig smtp.page-educ.fr. NS
Answer
The response has no answer records.
Authority
page-educ.fr. 3248 SOA ns1.gandi.net. hostmaster.gandi.net. 1772668800 10800 3600 604800 10800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0