When setting up Email Notifications, you can use the Subscribed Projects area to choose which sections to receive notifications on. When the Use Default Value checkbox is checked, the projects determined by the server administrator will be used:
When you uncheck this checkbox, you can select which projects you don't want notifications on by placing them in Available and which projects you do want notifications on by placing them in Selected:
If you want to be sure you are receiving notifications on new projects (that you are given read rights to) as they get created, make sure the Automatically include new projects as they become available checkbox is checked. If you want to selectively add projects yourself, uncheck this box.
This setting works in conjunction with the other Email Notification settings to determine when notifications will be sent. In particular, even if you leave all the available projects selected, you can confine notifications to specific projects based on how you configure sections used to filter notifications.
