mxalt.u-ga.fr has no CNAME records.
Question and response
Question
dig mxalt.u-ga.fr. NS
Answer
The response has no answer records.
Authority
u-ga.fr. 900 SOA eip1.u-ga.fr. dnsadmin.univ-grenoble-alpes.fr. 2020498344 1200 300 2419200 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0