DocumentItem Object (Outlook)
Represents any document other than a Microsoft Outlook item as an item in an Outlook folder.
A DocumentItem object is any document other than an Outlook item as an item in an Outlook folder. In common usage, this will be an Office document but may be any type of document or executable file.
Unlike other Outlook objects, you cannot create this object.
When you try to programmatically add a user-defined property to a DocumentItem object, you receive the following error message: "Property is read-only." This is because the Outlook object model does not support this functionality.