About Outlook for Windows Mail

Owned by Julie Wetherill
Last updated: Oct 12, 2016

Where does Outlook store email files?

The Outlook data directory is usually located:

In XP:

c:\Documents and Settings\[your login name]\Local Settings\Application Data\Microsoft\Outlook

In Vista and Windows 7:

c:\Users\[your login name]\AppData\Local\Microsoft\Outlook

How does Outlook store email files?

Outlook stores all mail directories, messages and attachments associated with an individual email account in an Outlook data file.  Inside the data file, Outlook stores attachments with their associated email message.  There are two types of Outlook data files -- Outlook data file (.pst) and offline Outlook data file (.ost). 

  • An Outlook data file (.pst) is used with POP3, IMAP, and web-based mail accounts.  A PST file is also used when you archive your email or back-up Outlook folders on your computer.
  • An offline Outlook data file (.ost) is used with MS Exchange mail accounts or with accounts set up to use Outlook Connector for Windows Live Hotmail. 

Both types of Outlook data file are proprietary binary files that can only be viewed by opening them in Outlook. 

There may be one or many Outlook data files (PST or OST).  Since Outlook supports multiple email account profiles, there could be multiple data files (one for each profile).  Data files created automatically by Outlook will be named with the prefix “Outlook” but may also be labeled with information about the email account. 

Examples of Outlook data file names:

Outlook.ost
Outlook0.ost
Outlook.pst
Outlookhulmail.harvard.edu-00000004.pst

Since Outlook allows the user to manually create additional PST files, there can be an arbitrary number of PST files present that do not include “Outlook” in the file name.  Some examples:

Transfer.pst
Saved.pst
November2009.pst

Lastly, Outlook has an auto archive function that when enabled will periodically archive older messages to a separate PST file called “Archive.pst”. 

Below is a sample Outlook data directory:

>c:\Users\[your login name]\AppData\Local\Microsoft\Outlook Archive.pst

Communications.pst

Default Outlook Profile.sharing.xml.obi

extend.dat

Myra.pst

outlook.bak

outlook.log

outlook.ost

schedules.pst

spscoll.dat

uanrdex.oab

ubrowse.oab

udetails.oab

updndex.oab

urdndex.oab

utmplts.oab

~last~.sharing.xml.obi