I think that you don't get it.
Mail indicator is applet for inboxes - per user - setup in My Control Panel (not admin panel).
In admin panel you've got Outgoing server settings, which is used to send error notifications, watchdog notifications etc. It's not related to user email accounts. If you've got system settings to send emails, then it's great, but in most cases you should setup some new account for this purpose or use one of the existing like admin, support, help, system, etc. Then click "Test" to test it. Always hit "Save" before test if you've changed something.