How Outlook Stores Your Data

Outlook is basically a flat-file database. As you create new e-mails, or as new e-mails are received, or when you create and save a new item in an Outlook folder, Outlook adds the new item to the location identified as the primary store. The exact location depends on how you configured Outlook when it was installed on your computer. Usually, your Personal Folders file (username.pst for example) is stored on your local computer in your ‘My Documents’ folder.

If you are not connected to an Microsoft Exchange Server, your e-mails, calendar, and other items are delivered to and stored locally in a personal folder (.pst) file. The letters pst stand for Personal Storage Table. The following files are commonly referenced by the various versions of Outlook.

Outlook data files (.pst)

drive:Documents and SettingsLocal SettingsApplication DataMicrosoftOutlook

Offline Folders file (.ost)

drive:Documents and Settings<>Local SettingsApplication DataMicrosoftOutlook

Personal Address Book (.pab)

drive:Documents and Settings<>Local SettingsApplication DataMicrosoftOutlook

Offline Address Books (.oab)

drive:Documents and Settings<>Local SettingsApplication DataMicrosoftOutlook

Outlook contacts nicknames (.nk2)

drive:Documents and Settings<>Application DataMicrosoftOutlook