Updated: 2009-07-23

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When a Microsoft Office Outlook 2007 account is configured to use Cached Exchange Mode, Office Outlook 2007 works from a local copy of a user's Exchange mailbox stored in an Offline Folder file (.ost) on the user's computer and with the offline address book (OAB). The cached mailbox and OAB are updated periodically from the Exchange server.

Cached Exchange Mode can only be configured for Microsoft Exchange Server e-mail accounts. Although Cached Exchange Mode is supported on Microsoft Exchange Server 2000 and later versions, we recommend that this feature be used with Exchange Server 2003 or a later version.

If you do not configure Cached Exchange Mode options, the current state of Cached Exchange Mode does not change for existing profiles when Outlook upgrades to a new version. If a user account was configured to use Cached Exchange Mode in Microsoft Office Outlook 2003, for example, Cached Exchange Mode is still enabled when the user upgrades to Office Outlook 2007. The location for new .ost or OAB files is the default location: For Windows XP, the location is %userprofile%\Local Settings\Application Data\Microsoft\Outlook; for Windows Vista, the location is %userprofile%\AppData\Local\Microsoft\Outlook.

When you consider whether to change Cached Exchange Mode settings for synchronization with Exchange servers, be aware that timing for Office Outlook 2007 has improved so that e-mail is updated faster than in Outlook 2003. However, there might be circumstances when you have to modify the default synchronization values.

You can configure several options for Cached Exchange Mode, including the default .ost file location for users in your organization that do not already have .ost files for Cached Exchange Mode and offline use. If you do not specify a different .ost location, Outlook creates an .ost file in the default location when users start Outlook in Cached Exchange Mode.

You can lock down the settings to customize Cached Exchange Mode by using the Outlook Group Policy template (Outlk12.adm). Or you can configure default settings by using the Office Customization Tool (OCT), in which case users can change the settings.

Configuring Cached Exchange Mode settings by using the Office Customization Tool

Configure Cached Exchange Mode settings by using the Office Customization Tool

  1. In the Office Customization Tool (OCT), in the tree view, locate the Outlook section, click Specify Exchange Settings, and then click Configure an Exchange Server connection.

    NoteNote:

  2. To specify a new location for users' .ost files, click More Settings, and then click Enable offline use. Enter a folder path and file name for the .ost file location. You can also enter a path in the Directory path to store the Offline Address Book files text box, and then click OK.

  3. To enable or disable Cached Exchange Mode, or to specify default download behavior when Cached Exchange Mode is enabled, on the Specify Exchange Settings page click Configure Cached Exchange Mode.

  4. Select the Use Cached Exchange Mode check box to enable Cached Exchange Mode for users. By default, Cached Exchange Mode is disabled if you do not select the check box but you do select Configure Cached Exchange Mode.

  5. Select a default download option if you enabled Cached Exchange Mode in step 4:

    • Download only headers: Users see header information and the beginning of the message or item body (a 256-KB plain-text buffer of information). Full items are downloaded by double-clicking to open the message or by clicking Download the rest of this message now at the bottom of the reading pane.

    • Download headers followed by the full item: All headers are downloaded first, and then full items are downloaded. The download order might not be chronological. Outlook downloads headers followed by full items in the folder that the user is currently accessing, and then downloads headers followed by full items in folders that the user has recently viewed.

    • Download full items: Full items are downloaded. The download order might not be chronological. Outlook downloads full items in the folder that the user is currently accessing, and then downloads full items in folders that the user has recently viewed.

  6. To turn off Headers Only mode, clear the On slow connections, download only headers check box. Downloading only headers is the default behavior when users have slow connections. There are scenarios in which Outlook perceives that users have slow connections when users' content throughput is fast, or vice versa. In these situations, you might want to select or clear this option.

  7. Choose to disable the downloading of shared non-mail folders as part of Cached Exchange Mode synchronizations to users' .ost files. By default, shared non-mail folders are downloaded. Downloading Public Folder Favorites could cause users' .ost files — if they use non-Unicode .ost files — to grow in size beyond the limit of 2-gigabytes (GB). This results in errors when Outlook synchronizes.

  8. Choose to download Public Folder Favorites as part of Cached Exchange Mode synchronizations to users' .ost files. By default, Public Folder Favorites are not downloaded. Downloading Public Folder Favorites could cause users' .ost files — if they use non-Unicode .ost files — to grow beyond the 2-GB size limit. This results in errors when Outlook synchronizes. Also, synchronizing Public Folder Favorites causes additional network traffic that might be unwelcome to users who have slow connections.

Configuring Cached Exchange Mode settings by using Group Policy

Customize Cached Exchange Mode options by using Group Policy

  1. In Group Policy, load the Office Outlook 2007 template (Outlk12.adm).

  2. To customize Cached Exchange Mode options, under the following paths, double-click the policy that you want to set. For example, double-click Use Cached Exchange Mode for new and existing Outlook profiles.

    • User Configuration\Administrative Templates\Microsoft Office Outlook 2007\Tools | Account Settings\Exchange\Cached Exchange Mode

    • User Configuration\Administrative Templates\Microsoft Office Outlook 2007\Tools | Account Settings\Exchange: The two Cached Exchange Mode options are Synchronizing data in shared folders and Cached Exchange low bandwidth threshold.

  3. Click Enabled and select an option (if appropriate).

  4. Click OK.

You can configure the settings shown in the following table for Cached Exchange Mode in the tree view of the OCT (User Configuration\Administrative Templates\Microsoft Office Outlook 2007\Tools | Account Settings\Exchange\Cached Exchange Mode).

Cached Exchange Mode option Description

Use Cached Exchange Mode for new and existing Outlook profiles

By default, users can decide to configure Cached Exchange Mode or use Online mode. By enabling this setting, new and existing Outlook profiles are configured to use Cached Exchange Mode. Disabling this setting configures new and existing Outlook profiles to use Online mode.

Do not sync in Cached Exchange Mode when users click Send/Receive or press F9

By default, when users click Send/Receive or press F9 for Cached Exchange Mode accounts, Outlook synchronizes with the Exchange server. When this setting is enabled, clicking Send/Receive and pressing F9 does not synchronize with Exchange unless only one folder is being synchronized. Users can continue to use shift-F9 to synchronize the current folder.

Enter seconds to wait to upload changes to server

Specifies the number of seconds to wait before uploading changes to the Exchange server.

The default upload wait time in Outlook is 15 seconds.

Enter seconds to wait to download changes from server

Specifies the number of seconds to wait before downloading changes from the Exchange server.

The default download wait time in Outlook is 5 seconds.

Enter maximum seconds to wait to sync changes

Specifies the maximum number of seconds to wait before uploading all changes with the Exchange server.

The default maximum wait time in Outlook is 60 seconds.

The following steps outline how the default upload timer and maximum wait timer interact:

  • If a local change occurs during the 15-second window of the upload timer, the upload timer restarts.

  • If no other local changes occur before the 15-second expires, the data is synchronized to the Exchange server.

  • If changes continue to occur before the 15-second expires, all changes are synchronized to the Exchange Server computer after 60 seconds, regardless of the number of seconds currently in the upload wait timer.

Cached Exchange Mode (File | Cached Exchange Mode)

Specifies the default Cached Exchange Mode for new profiles and disables the download options in the Cached Exchange Mode command submenu in the File menu. This applies only to Microsoft Exchange Server 2003 or later versions.

Disallow Download Full Items (File | Cached Exchange Mode)

Disables the download option Download Full Items in the Cached Exchange Mode download options menu. This applies only to Microsoft Exchange Server 2003 or later versions.

Disallow Download Headers then Full Items (File | Cached Exchange Mode)

Disables the download option Download Headers and then Full Items in the Cached Exchange Mode download options menu. This applies only to Microsoft Exchange Server 2003 or later versions.

Disallow Download Headers (File | Cached Exchange Mode)

Disables the download option Download Headers in the Cached Exchange Mode download options menu. This applies only to Microsoft Exchange Server 2003 or later versions.

Disallow On Slow Connections Only Download Headers (File | Cached Exchange Mode)

Disables the download option On Slow Connections Only Download Headers in the Cached Exchange Mode download options menu. This applies only to Microsoft Exchange Server 2003 or later versions.

Download Public Folder Favorites

Public Folder Favorites are synchronized to users' .ost files.

Download shared non-mail folders

By default, most shared folders that users access in other mailboxes are automatically downloaded and cached in the users' local .ost files when Cached Exchange Mode is enabled. Only shared Mail folders are not cached. You can use this setting to change this behavior so that non-mail folders are not downloaded automatically.

You can configure the settings shown in the following table for Cached Exchange Mode: Click User Configuration, click Administrative Templates, click Microsoft Office Outlook 2007, click Tools | Account Settings, and then click Exchange.

Cached Exchange Mode option in Exchange area Description

Synchronizing data in shared folders

Controls the number of days that elapse without a user accessing an Outlook folder before Outlook stops synchronizing the folder with Exchange.

Cached Exchange low bandwidth threshold

Specifies the bit rate threshold value below which Outlook will identify the network connection as a 'slow' connection.

If users in your organization do not already have .ost files, you might decide to configure a default .ost file location for Cached Exchange Mode and offline use. If you do not specify a different .ost location, Outlook creates an .ost location in the default location when users start Outlook in Cached Exchange Mode.

Configure a default .ost location by using Group Policy

  1. In Group Policy, load the Office Outlook 2007 template (Outlk12.adm).

  2. To configure a default .ost location, click User Configuration, Administrative Templates, click Microsoft Office Outlook 2007, click Miscellaneous, click PST Settings, and then double-click Default location for OST files.

  3. Click Enabled to enable the policy setting.

  4. In the text box, enter the default location for .ost files. For example:

    %userprofile%\Local Settings\Application Data\Microsoft\newfolder.

  5. Click OK.

You can define a new default location for both Personal Folder (.pst) and .ost files by using the setting Default location for PST and OST files.

If the Exchange Server version and settings support Unicode, you can require that new Outlook files be Unicode. For example, this can be helpful if users will require .ost files that have additional space to support large Exchange mailboxes when those user accounts are configured to use Cached Exchange Mode. For more information about how to configure user accounts in this scenario, see Plan a Cached Exchange Mode deployment in Outlook 2007.

Specify Unicode for new Outlook files

  1. In Group Policy, load the Office Outlook 2007 template (Outlk12.adm).

  2. Click User Configuration, click Administrative Templates, click Microsoft Office Outlook 2007, click Miscellaneous, and then in the reading pane double-click Preferred PST Mode (Unicode/ANSI).

  3. Select Enabled.

  4. In the Choose a default format for new PSTs, drop-down list select Enforce Unicode PST.

  5. Click OK.

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