* <pre>
     * message: Sent a test mail.
     * </pre>
     * @param property The property name for the message. (NotNull)
     * @return this. (NotNull)
     */
    public FessMessages addSuccessSendTestmail(String property) {
        assertPropertyNotNull(property);
        add(property, new UserMessage(SUCCESS_send_testmail));
        return this;
    }

    /**