How to Use Outlook Web Access Web Parts: Exchange 2007 Help:
Outlook Web Access Web Parts let you access Outlook Web Access content directly from a URL. The URL can be entered into a Web browser or embedded in an application. Generally, Web Parts are not created manually. Instead, they are created programmatically based on selections made in a user interface (UI), or they are embedded directly in an application, such as a Microsoft Office SharePoint Server 2007 page. The code behind the UI then creates the URL. One use for Outlook Web Access Web Parts is to display a user’s Inbox or Calendar in an Office SharePoint Server 2007 page.