To change the OST file to Unicode:

  1. Open Outlook and go to Tools > Account Settings. On the E-mail tab, double-click Microsoft Exchange.
  2. Click the More Settings button and go to the Advanced tab.
    Toward the bottom you will see the Mailbox Mode section. If it does not say "Outlook is running in Unicode mode", that means you are running Outlook in non-Unicode mode, which has a limit of 2 GB for the offline folder file (OST). Please continue with the following steps to change the mode.
  3. Uncheck the Use Cached Exchange mode option. When you see the message "You must restart Outlook for these changes to take effect," click OK.
  4. Click the Offline Folder File Settings button in the same window. In the Offline Folder File Settings window, copy the path to the OST file. Navigate to the folder where the file is located.
  5. Close Outlook.
  6. Delete the OST file that you found in step 4. (or rename it to .OLD)
  7. Start Outlook. It will start in online mode, without the offline file. This may be a bit slower than usual.
  8. Enable Cached Exchange Mode. (In Tools > Account Settings > Microsoft Exchange, select the Use Cached Exchange Mode option. Click OK, then Finish.)
  9. Start Outlook. At the bottom of the Outlook window, you can see that Outlook has started to download all messages from the server. This is part of the process for creating a new OST file.
  10. Verify that Outlook is running in Unicode mode. (Go to Tools > Account Settings > Microsoft Exchange > More Settings > Advanced tab. Under Mailbox Mode, you should see the status message "Outlook is running in Unicode mode against Microsoft Exchange".
  11. Please wait wait until the status in the lower-right corner says "All folders are up to date". This means that the new OST file has been created successfully.

Article ID: 125, Created On: 1/30/2013, Modified: 1/30/2013

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