Do not include Internet Calendar Integration in Outlook must be enforced.

The Internet Calendar feature in Outlook enables users to publish calendars online (using the webcal:// protocol) and subscribe to calendars that others have published. When users subscribe to an Internet calendar, Outlook queries the calendar at regular intervals and downloads any changes as they are posted. By default, Outlook allows users to subscribe to Internet calendars. If your organization has policies that govern the use of external resources such as Internet calendars, this feature might enable users to violate those policies.