The BlackBerry does not synchronize mail. It redirects mails recieved in monitored folders and reconciles deletes and reads. You will not get old messages. If you delete the user from the server, add the user back to the server, check those folders then wiped and reactivate the device you will get the all the messages in those folders from the last 5 days up to 200 messages by default. On the BES you could change that to 14 days and 750 messages. There is no way to get more than that.
