An ideal collaborative and messaging environment can be created using Microsoft Exchange Server and Microsoft Outlook. The Exchange Server stores all of the user mailboxes in a single database, called EDB (Exchange Database). A separate profile or mailbox is created for every user and it can be accessed through Outlook. An exact replica of user mailbox is stored on client system in the form of OST file. When you access data from Exchange Server, the Outlook synchronizes with Exchange Server and OST file automatically gets converted into PST. But in some cases, due to errors in OST file or in synchronization, the OST file can not be converted into PST and thus the stored data become inaccessible. To sort out such issues, you need to manually Convert OST to PST using third party applications.

In a practical scenario, when you attempt to start Microsoft Outlook or try to synchronize with Microsoft Exchange Server, you might come across the below given error message:

"Cannot open your default email folders. The file *.ost is not an offline folder file."

Here ‘*.ost’ is the name of your OST (Offline Storage) file, which is created by Microsoft Outlook when it was configured to work with Exchange Server. This file is created implicitly. This behavior renders your valuable data inaccessible and you need to go for OST Repair Tool to resolve this problem.

Grounds of the issue

There are two possible causes of this problem:

1-The OST file is corruption and Microsoft Outlook can not recognize this file and thus Outlook reports this error.
2-The OST file, associated with Exchange Server mailbox, can not be accessed by Outlook. This error generally occurs during synchronization.

In such situations, you need to take appropriate action as per the cause of the problem.

Resolution

If the problem is due to corruption to the OST file, go for OST Repair Tools and restore it. On the other hand, if the OST file can not be synchronized and converted into PST, Convert OST File into PST.

It is potential through third party applications, known as OST Repair Tool. These applications effectively convert all of the OST file objects into PST and make it accessible. After conversion, the resulted PST file can directly be imported into Microsoft Outlook and can be used to access data from Exchange Server.

Stellar Phoenix Mailbox Exchange Desktop is the most effective solution to convert your unusable OST file into usable PST file. It works well with Microsoft Outlook 2003, 2002, 2000, 98 and 97. This software is designed for 2003, XP, 2000, NT4 (SP6), ME and 98 SE.