Working with Outlook
You can use categories to organize your Outlook items (messages, contacts, tasks, whatever). Using categories, you'll be able to search for, sort, and group related items.
Outlook comes with a list of predefined categories. If none of them covers your requirements, you can create your own. Here's how:
Select an Outlook Item.
Select Categories from the Edit menu.
Click the Master Category List button.
Type the new category name in the New category: box.
Click OK twice.