Rectifying "Unable to start processing services" Error While Opening OST File

If you are using Microsoft Exchange Server in Cached Exchange Mode, it creates an OST (Offline Storage Table) file on client hard drive. The OST file is considered as slave replicas of server-based user mailbox. If the user mailbox or master copy is deleted, the slave-replica or OST file is orphaned. For proper working of collaborative messaging environment and accessing of user mailbox, OST to PST conversion takes place when you synchronize with Microsoft Exchange Server using Microsoft Outlook email client. In this case, the conversion is not possible.

In a practical scenario, you may encounter the below error message when you try to open Microsoft Outlook after Exchange Server mailbox corruption or after you make some changes to profile configuration:

"Unable to start processing services.
.ost cannot be accessed.
You must connect to your Microsoft Exchange Server computer at
least once before you can use your offline folder file."
If your original Exchange Server profiles is not modified, you can start Outlook with old OST file and extract data by moving your messages from the OST file to PST file. But, if your old profile is modified or deleted, the data in OST file cannot be accessed. At this point, you need to Convert OST to PST manually using appropriate tools.

The OST file becomes inaccessible after modifying the profile because of the security that works on the OST file, so that Microsoft Windows authentication cannot be used while you are working offline. Thus, you need to prove that you are authorized to logon to Exchange Server mailbox before you get local access of OST file.

For this purpose, an encrypted cookie is created by Exchange Server from unique entry ID of your mailbox when you successfully log onto Microsoft Exchange Server. The cookie is stored in Exchange Server profile.
In such critical situations, you need to first re-create the Exchange Server profile and then connect your Outlook data file to it. However, you cannot attach OST file to Exchange profile. You need to Convert OST File into PST before you can proceed.

Conversion is best possible using powerful and advanced OST PST conversion tools. The applications are capable of converting your orphaned and unusable OST file into a usable PST file, in all cases. They provide you an interactive graphical user interface to make the conversion process quick and simple.