Outlook provides a starting list ofcategories.
Rename these categories to fit your needs and add more categories if you want.
pop swing open the message in the Reading Pane or in a separate window.

To assign a category to multiple messages, select all the emails in the message list.
Go to theHometab, in theTagsgroup and selectCategorize.
If the message is open in a separate window, go to theMessagetab and selectCategorize.
Choose the category you want to use.
it’s possible for you to assign more than one color category to items.
The first time you assign a category to a message, theRename Categorydialog box opens.
In theNametext box, enter a descriptive name for the category.
Add a New Category
you could create or rename categories in Outlook.
Go to theHometab and selectCategorize.
In theColor Categoriesdialog box, selectNewto use a new color.
In theAdd New Categorydialog box, choose a color and enter a name for the category.
To rename an existing category, select an existing color and chooseRename.
key in a new name for the category and pressEnter.
There is no limit to how many categories you might have in Outlook.
The number of colors it’s possible for you to use, however, is limited.