Move an offline Outlook Data File (.ost)

When you use a Microsoft Exchange Server account account (required) and turn on offline support or use Cached Exchange Mode, a synchronized copy of your Microsoft Outlook items is saved in an offline Outlook Data File (.ost) in a hidden folder on your computer.

Where's my offline Outlook Data File (.ost)?

You can find your offline Outlook Data File (.ost) file through your Outlook account.

Important:  Don't use these steps to move an offline Outlook Data File (.ost) to another computer. When you add an Exchange account in Outlook on another computer and then work offline or use Cached Exchange Mode, an offline Outlook Data File (.ost) is created automatically and your Outlook data is downloaded.

  1. Do one of the following:

    • Open Outlook, and on the File tab, choose Account Settings > Account Settings > Data Files.

      or

    • Choose Start > Control Panel > Mail > Data Files.

      Mail Setup - Outlook dialog box that is accessed through Mail settings in the Control Panel

  2. On the Data Files tab, you'll see the location of the .ost file and can do one of the following:

    Data Files tab for Outlook Account Settings that shows location of outlook data files for a named user

    • Accept the offline Outlook Data File (.ost) location that appears in the Location column for the Exchange account.

      or

    • Change the location—for example, pick a different folder—where the offline Outlook Data File (.ost) file is to be saved.

      Notes: When you choose a new folder location, a new offline Outlook Data File (.ost) file is created automatically. Although it isn't necessary, you can manually move the existing file to the new folder to avoid the download time that is required to recreate the file.

      An offline Outlook Data File (.ost) also is used for the Outlook Connector. These files can't be moved.

Move or create an offline Outlook Data File (.ost)

Now that you've discovered the location—the full path—of your offline Outlook Data File (.ost), you can move it or create a new file.

  1. Open the Account Settings dialog box and choose the Data Files tab.

  2. Choose your Exchange account, and then choose Settings.

    In Account Settings, for an Exchange Account change data file settings

  3. On the Advanced tab, clear the Use Cached Exchange Mode check box, and choose OK.

  4. At the prompt, choose OK, and then choose Settings.

  5. On the Advanced tab, choose Outlook Data File Settings > Disable Offline Use > Yes.

    Note: If the Disable Offline Use button is unavailable, go back to step 3 and clear the Use Cached Exchange Mode check box.

  6. Choose Outlook Data File Settings, and then do one of the following:

    • I want to create a file (default)   
      Choose Browse, select the folder where you want to save the offline Outlook Data File (.ost), and then choose Open.

    • I want to move the old file   
      Choose Browse, select the offline Outlook Data File (.ost) that you moved to a new folder location, and then choose Open.

  7. Choose OK.

  8. On the Advanced tab, select the Use Cached Exchange Mode check box, choose OK, and then choose OK at the prompt to restart Outlook.

  9. Close the Account Settings and the Mail Setup dialog boxes.

  10. In the Mail dialog box, choose OK.

Note: When a new offline Outlook Data File (.ost) is created, the old file is not deleted. You can delete the old file.

Tips for opening Mail settings in the Control Panel

There are different paths you can take to get to Mail settings in the Windows Control Panel. The path you take might depend on which Windows operating system—32-bit or 64-bit—you're using, and which version of Outlook 2010 is installed.

Note: For Windows 10, in Control Panel, make sure the View by box in the upper-right corner is set to Category.

  • Choose Start > Control Panel > Mail.

    or

  • Choose Start and in the Search programs and files box, type Control Panel, and then choose Mail.

    or

  • Open the Control Panel, and in the Search box at the top of window, type Mail.

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