Use a policy to control PST files in Outlook

In Microsoft Outlook, users can create PST files or add new items to existing PST files. This article describes how to control these behaviors.

Important

This section, method, or task contains steps that tell you how to modify the registry. However, serious problems might occur if you modify the registry incorrectly. Therefore, make sure that you follow these steps carefully. For protection, back up the registry before you modify it so that you can restore it if a problem occurs. For more information about how to back up and restore the registry, see How to back up and restore the registry in Windows.

Prevent additions to an existing PST file

To prevent users from adding new data or content to an existing PST file, add the PSTDisableGrow registry entry, and then set the value to 1. Use the following steps:

1. Open Registry Editor.

2. Select either of the following registry subkeys depending on whether you want to deploy the setting through Group Policy (GPO) or the Office Customization Tool (OCT). Create the subkey if it doesn't exist.

   Type	Registry path
   GPO	HKEY_CURRENT_USER\Software\Policies\Microsoft\Office\16.0\Outlook\PST
   OCT	HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Outlook\PST

3. On the Edit menu, select New > DWORD Value.

4. Enter PSTDisableGrow, and then press Enter.

5. Right-click the PSTDisableGrow registry entry that you created, and then select Modify.

6. In the Value data box, enter 1, and then select OK.

Note

You can set the PSTDisableGrow registry entry to either of the following values:

• 0: Users can add new items to an existing PST file (default value).
• 1: Users can't add new content or data to an existing PST file.

Prevent the addition of new PST files

To prevent users from connecting a PST file to Outlook, add the DisablePST registry entry, and then set the value to 1. Use the following steps:

1. Open Registry Editor.

2. Select either of the following registry subkeys depending on whether you want to deploy the setting through Group Policy (GPO) or the Office Customization Tool (OCT). Create the subkey if it doesn't exist.

   Type	Registry path
   GPO	HKEY_CURRENT_USER\Software\Policies\Microsoft\Office\16.0\Outlook
   OCT	HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Outlook

3. On the Edit menu, select New > DWORD Value.

4. Enter DisablePST, and then press Enter.

5. Right-click the DisablePST registry entry that you created, and then select Modify.

6. In the Value data box, enter 1, and then select OK.

Note

You can set the DisablePST registry entry to any of the following values:

• 0: Users can add PST files (default value).
• 1: Users can't add PST files. However, in scenarios in which a PST file was connected to Outlook before this registry value was added, the existing PST file will remain connected. No new PST files can be added.
• 2: Users can only add PST files that are exclusively for sharing, such as SharePoint PST files.

Considerations for new Outlook

The Group Policy (GPO) and the Office Customization Tool (OCT) registry keys that are described in this article are traditionally used to control PST behavior in classic Outlook for Windows. However, they also affect PST functionality in new Outlook for Windows. This is because new Outlook for Windows relies on classic Outlook's MAPI components to interact with PST files.

Interaction with Exchange Online policies

If you run the Set-OwaMailboxPolicy cmdlet to set the OutlookDataFile parameter to Allow, Exchange Online policy normally allows users to open, import, export, and copy items to and from PST files. However, if some registry entries, shown in the following table, are set to 1, they override the Exchange Online policy for PST file actions in new Outlook clients.

Registry entries in classic Outlook	Symptoms in new Outlook
PSTDisableGrow	Users can't move mailbox items to a PST
PSTDisableGrow and PSTDisableGrowAllowAuthenticodeOverrides	Users can't remove PSTs from the mailbox
PSTDisableGrow and PSTDisableGrowAllowAuthenticodeOverrides	Users can't check PST content

Tip

If you intend to allow users to fully manage PST files in new Outlook clients by using the OWA mailbox policy (OutlookDataFile parameter set to Allow), ensure that the legacy registry keys, PSTDisableGrow and PSTDisableGrowAllowAuthenticodeOverrides, are either not configured, or are set to their default value (0). This will prevent unintended conflicts and ensure the desired PST file behavior.