To set up Outlook Subcategories

You can supplement Microsoft Outlook's built-in Categories field with your own Subcategory field, or use a category naming convention to allow you to better organize and group "subcategories" together. Method #1 | Method #2 | Method #3 | More Information Method 1 – Custom Keyword field Add a new Subcategory field to a folder like  

Changing the folder sort order in Outlook's Folder list

The Folder List is normally in alphabetical order. In Outlook 2010 and 2013, the Inbox, Drafts, Sent Items, and Deleted Items folders are grouped at the top of the folder list, with the user-created folders sorted alphabetically below.