By default, shared mail folders are downloaded in Cached mode in Outlook 2010 and Outlook 2013

By default, if a Microsoft Outlook 2010 or Microsoft Outlook 2013 profile is configured in Cached mode and you add another user’s mailbox or shared folder to your profile, all items in all the folders to which you have access in the shared mailbox are downloaded to your local cache. This is a change from Microsoft Office Outlook 2007, in which only shared non-mail folder items are cached by default.

For example, the following figure shows the shared Inbox folder of Guido Pica. This Inbox folder is being cached in Outlook 2010 because the status bar displays Connected when this folder is selected in the navigation pane.

This problem is caused by a change in the default shared folder caching behavior which was introduced in Outlook 2010.

To change the shared folder caching behavior in Outlook 2010 or Outlook 2013 to match the default behavior in Office Outlook 2007, you must add the following registry data to your Outlook client. In this situation, only non-mail folders such as the Calendar, Contacts, and Tasks folders are cached.


Note If you configure the registry value in the \Policies registry key, the change is applied to all existing Outlook profiles. If you configure the registry value in the non-Policies key, the change only applies to new Outlook profiles that you create.

You can use one of the following methods to configure this registry data for Outlook 2010 and Outlook 2013:

• Manually change the Windows Registry.
• Configure the registry by using a Group Policy setting.
• Deploy the Shared Mail Folder Cache setting by using the Office Customization Tool.

Regardless of the method that you use, if you disable the caching of shared mail folders, the Outlook status bar displays Online when you select a shared mail folder in another mailbox in the navigation pane. This is illustrated in the following figure.


In this configuration, items in mail folders are not available when you are working offline in Outlook. However, items in non-mail folders are still available when you are working offline in Outlook.

Method 1: Manual modification of the Windows Registry

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 added protection, back up the registry before you modify it. Then, you can restore the registry if a problem occurs. For more information about how to back up and restore the registry, click the following article number to view the article in the Microsoft Knowledge Base:

To change the shared folder caching behavior in Outlook 2010 and Outlook 2013 to match the default behavior in Office Outlook 2007, you must add a registry value to your Outlook client. To do this, follow these steps:

1. Exit Outlook.
2. Start Registry Editor:
   
   For Windows Vista and for Windows 7:
   1. Click Start
      Collapse this imageExpand this image

      
      , type regedit in the Start Search box, and then press ENTER.
      
      Collapse this imageExpand this image

      
      If you are prompted for an administrator password or for confirmation, type the password, or click Allow.
   For Windows XP:
   1. Click Start, click Run, type regedit, and then click OK.
3. Locate and then click the following registry key:
   HKEY_CURRENT_USER\Software\Microsoft\Office\xx.0\Outlook\Cached Mode
   Where xx.0 is 14.0 for Outlook 2010 and 15.0 for Outlook 2013.
   
   Note If the Cached Mode key does not exist, create this key by following these steps:
   1. Select the Outlook key.
   2. On the Edit menu, point to New, and then click Key.
   3. Type Cached Mode, and then press ENTER.
   4. Select the Cached Mode key and then go to step 4.
4. On the Edit menu, point to New, and then click DWORD Value.
5. Type CacheOthersMail, and then press ENTER.
6. On the Edit menu, click Modify.
7. Type 0, and then click OK.
8. Exit Registry Editor.
9. Start Outlook.

Note This method only affects any new Outlook profiles that you create. To change the behavior for all existing Outlook profiles, add the registry value in the following registry key path:

Method 2: Configure the registry by using a Group Policy setting

The registry key value that is required to change the default shared folder caching behavior in Outlook 2010 and Outlook 2013 can be configured by using a Group Policy setting.

Outlook 2010

The default Group Policy template (Outlk14.adm) for Outlook 2010 does not contain the policy setting that controls this functionality. Therefore, you must use a custom Group Policy template to manage this functionality.

To deploy this setting by using a custom Group Policy template, follow these steps:

1. Download the following file from the Microsoft Download Center:
   http://download.microsoft.com/download/2/1/F/21FB30E6-C526-4B65-BAF1-7FE0E2252879/outlk14-DisableCachingSharedMailFolders.zip

   (http://download.microsoft.com/download/2/1/F/21FB30E6-C526-4B65-BAF1-7FE0E2252879/outlk14-DisableCachingSharedMailFolders.zip)
   Note The custom .adm template contains the following text.

   CLASS USER
   
      CATEGORY !!L_MicrosoftOfficeOutlookCachedSharedMailFolders
            POLICY !!L_TurnOnOffSharedMailFolderCaching
                KEYNAME "Software\Policies\Microsoft\Office\14.0\Outlook\Cached Mode"
                EXPLAIN !!L_TurnOnOffSharedMailFolderCachingExplain
                VALUENAME "CacheOthersMail"
                VALUEON NUMERIC 0
                VALUEOFF NUMERIC 1
            END POLICY
         END CATEGORY
   [strings]
   L_MicrosoftOfficeOutlookCachedSharedMailFolders="Outlook 2010 Shared Mail Folder Caching"
   L_TurnOnOffSharedMailFolderCaching="Disable shared mail folder caching"
   L_TurnOnOffSharedMailFolderCachingExplain="This policy controls the caching of shared mail folders in Outlook 2010 \n \n By default, Outlook 2010 caches shared mail and non-mail (Calendar, Contacts, Tasks) to which you have access.\n \n Enable this policy to configure Outlook to only cache shared non-mail folders. This mirrors the default shared folder caching behavior in Outlook 2007.\n \n If you disable this policy or do not configure this policy, shared mail and non-mail folders to which you have access are cached in your .ost file when you add another mailbox to your profile."
   

2. Add the Outlk14-DisableCachingSharedMailFolders.adm file to the Group Policy Object Editor or to the Group Policy Management Console.
   
   Note The steps to add the .adm file to the Group Policy Object Editor or the Group Policy Management Console vary, depending on the version of Windows that you are running. Also, because you may be applying the policy setting to an organizational unit and not to the whole domain, the steps may also vary in this aspect of applying a policy setting. Therefore, check your Windows documentation for more information.
   
   Go to step 3 after you add the .adm template to the Group Policy Object Editor or to the Group Policy Management Console.
3. In the Group Policy Object Editor or the Group Policy Management Console, under User Configuration, expand Classic Administrative Templates (ADM) to locate the policy node for your custom template. By using the custom *.adm template that is provided in step 1, this node is named Outlook 2010 Shared Mail Folder Caching.
   
   Collapse this imageExpand this image

   
4. Under Outlook 2010 Shared Mail Folder Caching, double-click Disable shared mail folder caching.
5. Click Enabled, and then click OK.
   
   At this point, the policy setting is applied on your Outlook 2010 client workstations when the Group Policy setting update is replicated. To test this change, at the command prompt, type the following command, and press ENTER:
   gpupdate /force

After you run this command, start Registry Editor on the client workstation to make sure that the CacheOthersMail registry value exists on the client, and that it has a value of 0: If you see this registry data in the registry, the Group Policy setting was already applied to this client. Start Outlook 2010 to verify that this change is implemented.

Outlook 2013

The default Group Policy template files (Outlk15.admx and Outlk15.adml) for Outlook 2013 contain the policy setting that controls this functionality.

To deploy this setting by using the Outlook 2013 Group Policy template, follow these steps: 

1. Download the following file from the Microsoft Download Center:
   http://www.microsoft.com/download/details.aspx?id=35554

   (http://www.microsoft.com/download/details.aspx?id=35554)
2. Extract the admintemplates_32bit.exe or admintemplates_64bit.exe file to a folder on your disk.
3. Copy the Outlk15.admx file to the C:\Windows\PolicyDefinitions folder.
4. Copy the Outlk15.adml file to the C:\Windows\PolicyDefinitions\xx-xx
   
   where xx-xx is a Language Culture Name. For example, for English (US), the Language Culture Name is en-us. For more information about Language Culture Names, visit the following Microsoft web site:
   
   http://technet.microsoft.com/library/ee797784(v=CS.20).aspx
   (http://technet.microsoft.com/library/ee797784(v=CS.20).aspx)
   
   
   Note The .adml file must be copied from the correct language folder.
   
5. Start the Group Policy Object Editor or the Group Policy Management Console.
   
   Note Because you may be applying the policy setting to an organizational unit and not to the whole domain, the steps may also vary in this aspect of applying a policy setting. Therefore, check your Windows documentation for more information.
   
6. In the Group Policy Object Editor or the Group Policy Management Console, under User Configuration, expand Administrative Templates, expand Microsoft Outlook 2013, expand Outlook Options, and then click the Delegates node.
   
   
   Collapse this imageExpand this image

   
7. Under Delegates, double-click Disable shared mail folder caching.
8. Click Enabled, and then click OK.
   
   At this point, the policy setting is applied on your Outlook 2013 client workstations when the Group Policy setting update is replicated. To test this change, at the command prompt, type the following command, and press ENTER:
   gpupdate /force

After you run this command, start Registry Editor on the client workstation to make sure that the CacheOthersMail registry value exists on the client, and that it has a value of 0: If you see this registry data in the registry, the Group Policy setting was already applied to this client. Start Outlook 2013 to verify that this change is implemented.

Method 3: Deployment of the Shared Mail Folder Cache setting using the Office Customization Tool

You can use the Office Customization Tool (OCT) to deploy the Shared Mail Folder Caching setting.

Outlook 2010

To deploy this setting in Outlook 2010, use the Add registry entries option in the Office Customization Tool (OCT). To do this, follow these steps:

Note You must have an Enterprise edition of Microsoft Office 2010 to use the OCT. If you have a Retail edition of Office 2010, you receive the following error when you try to start the OCT:

1. Click Start
   Collapse this imageExpand this image

   
   , type cmd in the Start Search box, and then press ENTER.
2. At the command prompt, type the following, and then press ENTER:
   \\Server\share\Office2010\Setup.exe /admin
3. In the Select Product dialog box, click Create a new Setup customization file for the following product.
4. Select the Office product in the Select Product dialog box, and then click OK.
5. In the navigation pane of the OCT, click Modify user settings, and then click Add.
6. In the Add/Modify Registry Entry dialog box, make the following changes, and then click OK. 
   1. Root: HKEY_CURRENT_USER
   2. Date type: REG_DWORD
   3. Key: Software\Microsoft\Office\14.0\Outlook\Cached Mode
   4. Value name: CacheOthersMail
   5. Value data: 0
   The following figure displays these changes that were made in the Add/Modify Registry Entry dialog box.
   
   Collapse this imageExpand this image

   
   
   
   After you click OK in the Add/Modify Registry Entry dialog box, the OCT displays this registry data. This change is displayed in the following figure.
   
   Collapse this imageExpand this image

   
7. Complete any remaining tasks in the OCT, and then save your .msp file.
8. Deploy Office 2010 with this .msp file.

Note This method only affects any new Outlook profiles that you create. To change the behavior for all existing Outlook profiles, add the registry value in the following registry key path:

HKEY_CURRENT_USER\Software\Policies\Microsoft\Office\14.0\Outlook\Cached Mode

Outlook 2013

To deploy this setting in Outlook 2013, use the Office Customization Tool (OCT) built-in setting. To do this, follow these steps: 

Note You must have an enterprise edition of Microsoft Office 2013 to use the OCT. If you have a Retail edition of Office 2013, you receive the following error when you try to start the OCT:

1. Click Start
   Collapse this imageExpand this image

   
   , type cmd in the Start Search box, and then press ENTER.
2. At the command prompt, type the following, and then press ENTER:
   \\Server\share\Office2013\Setup.exe /admin
3. In the Select Product dialog box, click Create a new Setup customization file for the following product.
4. Select the Office product in the Select Product dialog box, and then click OK.
5. In the navigation pane of the OCT, click Modify user settings, expand Microsoft Outlook 2013, expand Outlook Options, and then click Delegates.
6. Double-click the Disable shared mail folder caching.
7. Click Enabled, and then click OK.
   
   After you click OK, the OCT displays this registry data. This change is displayed in the following figure.
   
   
   Collapse this imageExpand this image

   
8. Complete any remaining tasks in the OCT, and then save your .msp file.
9. Deploy Office 2013 with this .msp file.

Note This method only affects any new Outlook profiles that you create. To change the behavior for all existing Outlook profiles, add the registry value in the following registry key path:

HKEY_CURRENT_USER\Software\Policies\Microsoft\Office\15.0\Outlook\Cached Mode

Disable Download of All Shared Folders

You can disable the caching of all shared folders when you are using a Cached mode profile. This includes shared mail folders and shared non-mail folders. This setting is available in the OCT and in the Group Policy template. 

The following figure shows the OCT setting that controls the caching of all shared folders in Outlook 2010.



When you use the OCT to disable this setting, the following registry key value is configured on your Outlook client. The following figure shows the Group Policy Management Editor setting that controls the caching of all shared folders in Outlook 2010.


When you use a Group Policy setting to disable this setting, the following registry key value is configured on your Outlook 2010 client.

Effect on the size of the Offline Outlook Data (.ost) file

If Outlook is configured to download shared folders, the contents of the shared folders are stored in your local Offline Outlook Data (.ost) file. If the shared folders contain many items or large attachments, your .ost file size may grow significantly.

Additionally, Outlook 2013 introduced support for Site Mailboxes. The Site Mailboxes feature requires Exchange Server 2013 and SharePoint 2013. If you are working in an Exchange 2013/SharePoint 2013 environment and are granted permission to a site mailbox, the site mailbox is automatically added to your Outlook 2013 client. If you have Download Shared Folders enabled, the site mailbox contents are synchronized to your local .ost file. This can result in a significantly larger .ost file.

For more information about large Outlook data files and performance, click the following article number to view the article in the Microsoft Knowledge Base:If the size of your .ost file is restricted by policies, caching shared folders may result in the .ost file size limit being reached. For more information about policies that administrators may use to limit the size of Outlook data files, click the following article number to view the article in the Microsoft Knowledge Base: