You can open folders in the offline folder (.ost) file, but cannot synchronize them with the Exchange server, or encounter various synchronization error messages shown in the synchronization log in the Deleted Items folder.

Precise Explanation:

This error means your OST file is corrupt, or one or more email messages in the OST file are damaged and the synchronization process cannot correct them.


If it is one or several erroneous email messages that cause the error, then sometimes you can simply delete these messages to solve the error. Also Microsoft provides the OST Integrity Check tool that can fix some minor synchronization errors as well. However, for most cases, the best solution to prevent data loss and further errors is using DataNumen Exchange Recovery, as follows:

  1. Close Microsoft Outlook and any other application that may access the OST file.
  2. Find the OST file that causes the error. You can determine the file location based on the property displayed in Outlook. Or use the Search function in Windows to search for the OST file.
  3. Recover the offline data in the OST file. The Exchange OST file contains offline data, including the mail messages and all other items, in your Exchange mailbox, which are very important to you. To recover and rescue these data, you must use DataNumen Exchange Recovery to scan the OST file, recover the data in it, and save them into an error-free Outlook PST file so that you can access all the messages and items with Outlook easily and efficiently.
  4. Backup the original OST file. For the sake of safety, you’d better backup it.
  5. Rename or delete the original OST file.
  6. Fix the error. Make sure the settings for the Exchange email account in Outlook are correct, and Outlook can connect to your Exchange server successfully. Then restart Outlook and send/receive your emails on the corresponding Exchange mailbox, which will let Outlook create a new offline folder file automatically and synchronize its data with the Exchange mailbox.If this method doesn’t work, then your current mail profile is incorrect, and you must delete it and create a new one, as follows:
    • 6.1 Close Microsoft Outlook.
    • 6.2 Click Start, and then click Control Panel.
    • 6.3 Click Switch to Classic View if you are using Windows XP or higher versions.
    • 6.4 Double-click Mail.
    • 6.5 In the Mail Setup dialog box, click Show Profiles.
    • 6.6 Select one of the incorrect profile in the list and click Remove to remove it.
    • 6.7 Repeat 6.6 until all incorrect profiles have been removed.
    • 6.8 Click Add to create a new profile and add email accounts according to their settings on the server.
    • 6.9 Start Outlook and re-synchronize your Exchange mailbox, you will find the problem disappear.
  7. Import the data recovered in step 3. After your OST file problem is solved, keep the new OST file for the Exchange mailbox open, and then open the PST file generated in step 3 with Outlook. As it contains all the recovered data in your original OST file, you can copy required items to your new OST file as needed.