Administrateur can be param the acknowledgement of delivery mail object and body.

app/controllers/admin/mails_controller.rb

@@ -0,0 +1,20 @@
+class Admin::MailsController < AdminController
+  before_action :retrieve_procedure
+
+  def index
+
+  end
+
+  def update
+    mail = current_administrateur.procedures.find(params[:procedure_id]).mail_templates.find(params[:id])
+    mail.update_attributes(update_params)
+
+    redirect_to admin_procedure_mails_path
+  end
+
+  private
+
+  def update_params
+    params.require(:mail_received).permit(:body, :object)
+  end
+end