A <default> action list is automatically generated when you create an alert policy. You cannot delete or rename it. The <default> action list lets you specify a list of actions to be performed for every alert that is raised, acknowledged, and cleared that does not match a specific action list (while the alert policy is active). These actions are performed in addition to any global actions specified in the same alert policy.

Add actions to the <default> action list and enable and disable it as you would any other action list. See Action List Properties for more information.