Different methods to change Outlook OST file location using Group Policy

MS Outlook has maintained its strong position as the email management system due to its ability to work in offline mode. If the email server is not accessible, then it does not mean that your mailbox will not work. You can access your emails and create new emails that will remain in Outbox until the connection is restored. For Exchange Server users, the offline mode is achieved through Exchange cached mode that creates an Offline storage file (OST) that will keep the mailbox accessible for offline usage.

By default, the OST file is saved in the local system at a predefined location-

  • C:\Users\AppData\Local\Microsoft\Outlook
  • C:\Documents and Settings\Local Settings\Application Data\Microsoft\Outlook

But, there are some recommendations related to the size of OST file that require to change the location of OST file due to its size issues.

  • In cached Exchange mode, the size of the offline storage table file is 50 to 80 percent large than a normal mailbox in on-premises Exchange Server. The format that Microsoft uses to store offline data is less storage efficient.
  • The maximum storage limit of OST file is 50 GB and you should make sure that the drive has sufficient space to keep the data file.

Due to the large size of OST file, you may require extra space to save the new contents and that’s why you require to change the location of OST file to another drive with more storage.

How to change the OST file location in Outlook?

You cannot change the location of OST file abruptly, but a Group Policy Template and Office customization tool can help you in changing the location while maintaining the integrity of data.

  1. First, download the Office Customization tool from the following URL location –
  2. Click Download option.
    Click Download option

The tool contains the Group Policy Administrative Templates to make the necessary changes in Outlook environment including the location of OST file too.

  1. Load the Outlook 2019/2016/2013 template in Group Policy.
  2. Open Group Policy Management Console (GPMC) > Domains > Group Policy Objects.
  3. Choose the Group Policy Objects that you want to change, right-click and choose Edit. The Group Policy Manager Editor will open.
  4. In the tree view, open User Configuration.
  5. Go to Policies and click Administrative Templates.
  6. Choose Microsoft Outlook 2019/2016/2013, then click Miscellaneous and PST Settings.
  7. Double-click on the option ‘Default location for OST files.’
  8. Click Enable.
  9. There will be a ‘Default location for OST files’ option in which you can input the default location of OST file that we mentioned earlier in the article.
  10. Click OK.
  11. Now, you can change the location of OST file from a different drive or folder. It will change the location without making the mailbox inaccessible.

If you do not want to create OST file during upgrade, then you can create another policy too.

  1. Load the Outlook 2019/2016/2012 template in the group policy.
  2. Open Group Policy Management Console (GPMC)>> Domains>>Group Policy Objects.
  3. Right-click on the policy object and click Edit option. The Group Policy Management Editor will open.
  4. Expand the following folder till Exchange option comes up – User Configuration > Policies > Administrative Templates > Microsoft Outlook 2016 > Account Settings.
  5. Double click on the option ‘Do not create new OST file on upgrade.’
  6. Click Enabled to create the group policy setting and click OK.

In Cached Exchange Mode, there are several settings that can help you in managing Outlook better and keep the behavior of mailbox in check. Some of the settings are Cached Exchange Mode Sync Settings, Disallow Download Full Items, Disallow Download Headers, Disallow Download Headers Then Full Items, Disallow On Slow Connections Only Download Headers, Download Public Folder Favorites, Download shared non-mail folders, and Use Cached Exchange Mode for new and existing Outlook profile.

These settings will help you in changing the group policies suitable to you.


Group Policy settings can help you in changing the location of OST file while remaining connected to the mailbox in a useful method to manage large sized OST file. But if the OST file is corrupt, then changing the location will not bring the desired results. For a corrupt OST file, you should use a professional OST to PST Converter software that can recover the items and save them in new data file.

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As soon as the data is recovered from a single or multiple OST file, then you should import it into Outlook to access it.

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