Yes, you can just reply to the email notification (see my previous message) and it will post to the forums automatically.
Well, i still don't quite understand your issue.. So you don't want clients A, B, C, D to access Admin Console? Usually only admin username is allowed to login to Admin Console. You can modify openfire.xml and add more users (probably what you did with efendi username). So A, B...etc. can't login to Admin Console with their usernames. If you want them not to access Admin Console page at all, then as i said, you can block it with firewall. This is up to you how to block such access and we can't help you here.