When you open more than one Personal Folders file (.pst) simultaneously in Microsoft Outlook, it can be difficult to distinguish which set of folders belongs to a particular .pst file. This is because all .pst files, by default, are named and appear in the Navigation Pane as Personal Folders.
To help distinguish the .pst files, you can change the default name of Personal Folders to something unique and recognizable to you. You can do this when you create a new .pst file or when the .pst file is open and displayed in the Outlook Navigation Pane.
Introduction to working with multiple .pst files
When you want to save Office Outlook items on your computer, a Personal Folders file (.pst) file is used. You can open and display the items from one or more .pst files simultaneously.
Many people use only one .pst file, and the default name of the top-level folder that appears in the Navigation Pane, Personal Folders, works without any problems. However, if you create multiple .pst files and do not change the default name, you will see the same top-level folder name, Personal Folders, for each .pst file that is open. This can make it difficult to know what set of folders belongs to which data file.
Why would you need two .pst files? There are a number of scenarios, including archiving older items, moving items to a second .pst file to reduce the size of a file, archiving your Sent Items to a separate .pst file, or working with projects that generate large numbers of e-mail messages.
NOTE If you use the AutoArchive feature in Outlook, the additional .pst file that is created to store older items does not use the top-level folder name Personal Folders. It is named Archive Folders.
Change the name of an existing Personal Folders folder in the Navigation Pane
NOTE This folder will always be a top-level folder in the Navigation Pane, in Mail.
This is the name that will appear as the top folder name in the Outlook Navigation Pane. Specifying a display name helps you to distinguish between the Outlook data files when you work with more than one .pst file. We recommend that you type a name that is unique and meaningful to you.
Click OK twice.