An Outlook 2003 cached offline folder file is created in ANSI format instead of in Unicode format in Exchange 2003 or in Exchange 2000

After you move your Microsoft Exchange Server 5.5 mailboxes to a computer that is running Microsoft Exchange Server 2003 or Microsoft Exchange 2000 Server, a user's offline folder (.ost) files and offline Address Book files remain in American National Standards Institute (ANSI) format. You expect the offline folder file and the offline Address Book file to be downloaded in Unicode format.

If you re-create a user's Microsoft Outlook profile and then obtain and synchronize a new offline folder file with the user's offline Address Book file, the offline folder file and the offline Address Book file use Unicode format.

In Exchange Server 5.5, a cached offline folder (.ost) file is created in ANSI format. This file has a two gigabyte (GB) size limit. Additionally, because this file is in ANSI format, the offline Address Book file also uses ANSI format.

When you move the mailboxes from your Exchange Server 5.5 computer to a computer that is running Exchange 2003 or Exchange 2000, the cached offline folder files that are in ANSI format are not automatically re-created in Unicode format.

To resolve this issue, enforce the use of Unicode for Microsoft Office Outlook 2003 by using Group Policy. To do this, follow these steps:

1. Install the Microsoft Office 2003 Editions Resource Kit.
2. On a domain controller, start the Active Directory Users and Computers snap-in.
3. Right-click the domain or organizational unit container where you want to configure the Group Policy object, click Properties, and then click the Group Policy tab.
4. Add a new Group Policy object, or edit an existing Group Policy object.
5. In the Group Policy Object Editor tool, expand User Configuration, right-click Administrative Templates, and then click Add/Remove Templates.
6. Click Add, click OUTLK11.ADM, click Open, and then click Close.
7. Under User Configuration, expand Administrative Templates, expand Microsoft Office Outlook 2003, and then click Exchange Settings.
8. In the right pane, double-click Exchange Unicode Mode - Ignore OST Format.
9. Click Enabled, and then click one of the following options in the Choose whether existing OST format determines mailbox mode list:
   • Create new OST if format doesn't match mode
   • Prompt to create new OST if format doesn't match mode
10. Click OK, and then quit the Group Policy Object Editor tool.

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:

In Exchange 2003 or in Exchange 2000, the offline Address Book remains in ANSI format if the offline folder file is in ANSI format. Therefore, in a typical Exchange site consolidation scenario, the following sequence of events may occur:

1. You move from an ANSI offline folder file and an ANSI offline Address Book scenario to Exchange Server 2003 or to Exchange 2000 Server.
2. Users download an offline Address Book in ANSI format.
3. You enforce a Unicode file format for the offline folder file.
4. Users download a full offline folder file in Unicode format.
5. Users download an offline Address Book in Unicode format.

The Outlook administrative template file that is described in the "Resolution" section exposes the following registry subkey:You can assign one of the following data values to the IgnoreOSTFormat registry value:

• A value of 0 corresponds to the default Group Policy option OST Format determines mode. This setting indicates that the current OST format is kept. For example, if an OST is in ANSI format, then it is kept in ANSI format.
• A value of 1 corresponds to the Group Policy option Create new OST if format doesn't match mode. This setting indicates that the OST format change is mandatory and cannot be delayed.
• A value of 2 corresponds to the Group Policy option Prompt to create new OST if format doesn't match mode. This setting indicates that the user will be allowed to delay the upgrade of the OST. The user will be prompted to upgrade the OST each time Outlook is launched but will allow the unmatched OST to be used.

To obtain the Microsoft Office 2003 Editions Resource Kit, or for additional information about the template files that are included with this resource kit, visit the following Microsoft Web site:For additional information about how to manage user configurations by using Group Policy, visit the following Microsoft Web site: