The common notification rule is a global email notification rule which you can create and choose to serve as a default one for all newly created projects.

The common notification rule is overridden by project-level notifications rules. See Project email notifications for details.
Enabling/Disabling Common Notification Rule
To edit/disable a default notification rule (enabled by default):
- Log in as Administrator (or a user who has the ‘Manage System Settings’ permission). If you are already logged in, skip this step.
- Click through User menu | Settings | Notifications on the header menu.
- Select the Common notification rule tab.
- To disable: Clear the 'Make Common Notification Rule available in all projects' checkbox, or
- To edit: Make changes as required. On the Notify creator option, see below.
- You can select one of the 3 preset event selections: Key events, Nothing, or All(default).
- Click 'Apply'.
Use the same process to enable the default notification rule.
The Always Notify Object Creator option
Messages and attachments added (created) by a user are not covered by this option. In other words, if you are the creator of a message or attachment, and this option is enabled, you will not be notified of the event of creating those.