Using Custom Categories
The power of this feature does not come from assigning pretty colors to a category. It comes from how you can use categories to find, sort and manage content.
It is most common to apply categories to messages, but calendar items, contacts, Tasks, Journal entries, and even RSS Feed items. Categories can be used to create search folders, discovery, or even apply Outlook rules. Outlook rules can in turn be used to assign categories. Objects are also not limited to one category. Figure 5 shows an email with two categories assigned. They are represented by the colored bars across the top. Calendar items are also colored based on categories applied to them.
Search folders query the entire mailbox based on filter settings, including category. They are a great way to leverage the power of categories. Outlook even offers a quick method of creating search folders based on category. One of the options under the Category button is 'Create category search folder'. This open the new search folder dialog window already at the categorized mail option.