Moving an Outlook offline data file (*.ost)

Last reviewed on April 10, 2014

While it's usually not necessary to relocate the offline cache used by an Exchange account, it is possible to move it to another folder or partition. For the most part, it only makes sense to move it if the C: drive is full.

Outlook 2013 IMAP and EAS (Outlook.com/Hotmail) ost files are moved using the ForcePSTPath key.

Moving the offline cache so its easier to back it up is generally pointless: it's an offline copy of your Exchange mailbox and it can only be opened by the account that created it. If you try to use an old cache file, Outlook will complain that it doesn't match the server mailbox. If the server fails and there is no server backup, the contents of the current, most up-to-date *.ost should be used to repopulate the server. In short, if you want a usable backup of your mailbox, export the contents to a *.pst file instead of including the *.ost in a backup file.

If you need to recover data from an orphaned ost file, I have a list of commercial recovery software listed at Convert an Offline File (.ost) to a Personal File (.pst)

With that disclaimer out of the way, if you do need to relocate the offline file, you can move it using the following steps.

If you are moving an .ost file, you need to create the ForceOSTPath registry value before adding the account to your profile.

Move the *.ost in Outlook 2010 and older

In Outlook 2010 and older, you can move the ost used by cached Exchange to another location by disabling offline mode then changing the path on the Advanced tab of the Exchange account properties.

If you want to move the ost before you create a profile, use the ForceOSTPath registry value.

Move the cached Exchange ost file in Outlook 2010 and older

  1. Open Account Settings
  2. Click More Settings (1)
  3. Deselect Use Cached mode (2) and click Apply.
  4. You can close Outlook and move the ost file now. If you want to create a new .ost file, you can skip this step.
  5. Click Outlook Data File button (3)
  6. Disable offline use (4) if Browse button is not enabled
  7. Click Browse button to select moved ost file (5)

Move the *.ost in Outlook 2013

The above method does not work with Outlook 2013. When you try to change the location of the offline file (.ost) in Outlook 2013, the Browse button is disabled.

You need to use one of two methods to move the ost file and both involve a new profile. If you are making a new profile, you can use ForceOSTPath registry key. Or you can move the .ost file and create a new profile in the Control panel, Mail applet and point it to the new location.

  1. Copy your .ost file to the new location. You can skip this step if you want to create a new .ost file.
  2. Open the Control panel, find Mail
  3. Click Show Profiles
  4. Click Add
  5. Control panel, mail dialog

  6. Type a name for your new profile, click OK
  7. Enter your username and password and let Outlook find your account information
  8. Select the Change account settings option, and then click Next
  9. Change Account Settings

  10. Click More Settings (1)
  11. move ost in Outlook 2013

  12. On the Advanced tab, click Outlook Data File Settings. (2)
  13. Click Browse (3), browse to the .ost file that you copied in step 1, and then click Open.
  14. If you want to create a new .ost file, browse to the new location, enter a filename, and then click Open. Outlook will create the new .ost file.
  15. OK your way back to the Mail profile dialog
  16. Click Always use this profile (shown in second screenshot), select the new profile that you created, and then click OK to close the dialog

Tip: You can jump to the ost location in Windows XP, Vista, or Windows 7/8 by typing or pasting this command into the address bar of Windows Explorer and pressing Enter:
%USERPROFILE%\Local Settings\Application Data\Microsoft\Outlook

 

Using ForceOSTPath to set the file location

The ForceOSTPath key is supported by Outlook 2003 and up, but applies only to new profiles (or in the case of Outlook 2010 and 2013, to new accounts in a profile).

You need to set this key before you add the account to your profile.

Open the registry editor and browse to this key (create it if it doesn't exist). Create a string value named ForceOSTPath and add the path. (You can use variables if you are using group policy to push it out to your users.)

Outlook 2013

HKEY_CURRENT_USER\Software\Microsoft\Office\15.0\Outlook
Expandable String Value: ForceOSTPath
Value data: full path you want to use

Outlook 2010

HKEY_CURRENT_USER\Software\Microsoft\Office\14.0\Outlook
Expandable String Value: ForceOSTPath
Value data: full path you want to use

Outlook 2007

HKEY_CURRENT_USER\Software\Microsoft\Office\12.0\Outlook
Expandable String Value: ForceOSTPath
Value data: full path you want to use

Outlook 2003

HKEY_CURRENT_USER\Software\Microsoft\Office\11.0\Outlook
Expandable String Value: ForceOSTPath
Value data: full path you want to use

Common variables

VariableTypical value (May vary)
%APPDATA%C:\Users\{username}\AppData\Roaming
%LOCALAPPDATA%C:\Users\{username}\AppData\Local (default for OST files)
%USERPROFILE%C:\users\{username}
%WINDIR%C:\Windows

More Information

The steps to move IMAP, POP, Sharepoint or Internet calendar pst files are similar, but cache files used by the Outlook Connector can't be moved. Outlook 2007, 2010, and 2013 support the ForcePSTPath registry value, which changes the default *.pst path for POP3, IMAP, and SharePoint data files. See How to move the IMAP personal folder (*.pst) for more information.

Written by

Diane Poremsky
A Microsoft Outlook Most Valuable Professional (MVP) since 1999, Diane is the author of several books, including Outlook 2013 Absolute Beginners Book. She also created video training CDs and online training classes for Microsoft Outlook. You can find her helping people online in Outlook Forums as well as in the Microsoft Answers and TechNet forums.

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