Here is the result of muyinvestigation :
Actually, the problem was coming from a bad right on a AD Exchange’s object.
A “Deny all” was set on the advance rights of the following objet :
CN=Public Folders,CN=Folder Hierarchies,CN=Premier groupe administratif,CN=Administrative Groups,CN=siege,CN=Microsoft Exchange,CN=Services,CN=Configuration,DC=siege,DC=local
I hope this can help someone.
Thanks and regards