Office Items enable you to take data from any external data source and map it directly to properties within your Office applications. SharePoint Server allows you to map the following items:
After you have this data in Outlook, for example, you can work with the items using the native capabilities of Outlook. You can also take additional data, although you are limited to four additional fields. If you need to create an Outlook Item Type with more than four custom fields, you need to create the full solution using Visual Studio.