How to Disable Caching in Outlook for Shared Mailboxes?

When you configure Outlook with an Exchange Server or Microsoft 365 account, the Cached Exchange Mode is enabled by default. This mode enables you to have a better experience as a copy (OST file) of your mailbox data is saved locally on your computer.

This offline OST file offers quick access to your mailbox data and is frequently updated with the mailbox on server.

When Cached Exchange Mode is enabled, by default, a local copy of the shared mailboxes (shared folders), in addition to other mailbox data, is also downloaded on your computer. Downloading all the data to the OST file increases the size of the OST file (cached copy).

A large OST file can cause performance issues in Outlook. To prevent such issues, you can avoid downloading all the data to the locally saved OST file. For this, you can only disable caching of shared mailboxes in Outlook, instead of disabling the Cached Exchange Mode for the whole account. In this article, we will discuss different ways to disable caching for shared mailboxes in Outlook. 

Ways to Disable Caching for Shared Mailboxes in Outlook 

Here are some ways to disable the caching for shared mailboxes in Outlook.

• Disable Shared Mailboxes Caching via Outlook Settings

You can turn off caching for shared mailboxes by disabling the Download Shared Folders option in Outlook. Follow these steps depending on your Outlook version: 

In Outlook 2007

1. Open Outlook 2007 and go to Tools > Account Settings.
2. Click on the Email tab and select your email profile.
3. Click Change and then click More Settings.
4. Under the Advanced tab, uncheck the Download Shared Folders option.
5. Click Apply > OK.
6. Restart Outlook for the changes to take effect.

In Outlook 2010

1. In Outlook 2010, go to File > Account Settings > Account Settings.
2. Select the Email tab and choose your email profile.
3. Click Change.
4. Go to More Settings and then select the Advanced tab.
5. Uncheck the Download Shared Folders option.
6. Click Apply > OK.
7. Restart Outlook for the changes to take effect.

In Outlook 2013, 2016, 2019, and 2021

1. Open Outlook, click on File > Account Settings > Account Settings.
2. Double-click on your email profile and click More Settings.
3. Go to the Advanced tab.
4. Uncheck the Download Shared Folders option and click OK.
5. Restart Outlook for the changes to take effect.

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• Disable Cached Exchange Mode via Registry Editor

You can use Registry Editor to disable caching in Outlook, including the caching for shared mailboxes. Here’s how you to do it: 

1. Press the Windows key + R to open the Run dialog box.
2. Type regedit and click OK to open the Registry Editor.
3. In the Registry Editor window, navigate to the following location:

HKEY_CURRENT_USER\Software\Microsoft\Office\VERSION\Outlook\Cached Mode

Note: Replace “VERSION” with the version of Outlook installed on your system. Refer to the below table for more details. If the Cached Mode key doesn’t exist, you can create it by right-clicking on the Outlook folder and selecting New > Key.

Outlook	Version
Outlook 2010	14.0
Outlook 2013	15.0
Outlook 2016	16.0
Outlook 2019	16.0

1. Create a DWORD registry named CacheOthersMail.
2. Double-click on CacheOthersMail and set its value to 0 (zero). Click OK.
3. Close the Registry Editor.

• Disable Cached Exchange Mode via Group Policy (GPO) 

You can also disable the Cached Exchange Mode via Group Policy if you’ve admins rights. Follow these steps to disable cached exchange mode via Group Policy: 

• Download the Administrative Template files (ADMX/ADML) for the Outlook version you’re using in your organization and extract them.
• Copy the Outlkxx.admx file (replace “xx” with the Outlook version) to the C:\Windows\PolicyDefinitions directory.
• Copy the Outlkxx.adml file to the C:\Windows\PolicyDefinitions\en-US folder.
• Open Group Policy Management.
• Right-click on the Organizational Unit (OU) where you want to apply the policy.
• Select “Create a GPO in this domain, and Link it here.”
• Provide a descriptive name for the policy and click OK.
• Right-click on the newly created GPO and select Edit.
• Now, go to User Configuration > Policies > Administrative Templates > Microsoft Outlook 201x > Outlook Options > Delegates to create a GPO.
• Find and double-click on the Disable shared mail folder caching policy.
• Select the Enabled option.
• Click Apply and then OK to save the changes.
• Close the Group Policy Management Editor.
• The GPO will be automatically applied to the specified OU.

Users within the OU will have caching for shared mailboxes disabled according to the policy settings.

How to Enable Caching in Outlook for Shared Mailboxes?

Cached mode is enabled by default in Outlook if you’re using an Exchange Server or Microsoft 365 account. However, if this option is disabled, you can enable it by following these steps:

1. Launch Outlook (2013 or later) and click the File tab.
2. Select Account Settings and then choose Account Settings from the dropdown menu.
3. In the Account Settings window, navigate to the Email tab.
4. Select the email account and click Change.
5. In the Change Account window, under Offline Settings, ensure that the option Use Cached Exchange Mode is checked.
6. Click Next and then click Finish. 

This will enable the caching for shared mailboxes and other mailbox data in Outlook. 

Conclusion

You can disable the caching for shared mailboxes in Outlook to prevent the OST file from growing large. To disable the caching for shared folders, you can follow the methods mentioned in this article.

In case your large OST file becomes inaccessible due to large size or any other reason, you can use an advanced OST to PST converter tool, like Stellar Converter for OST to extract data from the file.

This tool is capable of extracting all the mailbox data from orphaned or inaccessible OST files and saving it to PST format with precision.

It also offers option to export the extracted email items directly to existing Outlook profile, Office 365, or live Exchange Server without compromising data integrity. It supports Outlook 2021, 2019, 2016, and earlier versions.