Resolving error- “File *.ost is not an offline folder file.”

Microsoft Exchange Server and Microsoft Outlook are the applications that can create an ideal collaborative e-communication environment at a workplace. Exchange Server stores all the user mailboxes data in a single database file, termed as EDB (Exchange Database) file. A separate profile or mailbox is created for every user and it can be accessed through Outlook.

A copy or an exact replica of the same user mailbox data is stored on user’s system in the form of OST file. This way, whenever you access data from Exchange Server, the Outlook profile synchronizes with Exchange Server. This way the OST file automatically gets converted into PST file. However, in some cases, due to errors in OST file or in synchronization, the OST file gets converted to PST file format. Thus, the stored data becomes inaccessible. In order to sort out this issue, you have to manually perform ost to pst conversion. Else you can perform ost to pst conversion using a third party application.

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

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

Over here ‘*.ost’ is the name of your OST (Offline Storage) file, created with Microsoft Outlook when it was employed to work in compliance with Exchange Server. The OST file is created completely. The behavior results in inaccessibility of valuable data in the database and so you might have to go for OST repair tool to resolve this issue.

There can be two supposed reasons behind this issue, these are mentioned below:

1. Quite possibly, ost file is corrupt and MS Outlook is not able to recognize the file which is why Outlook reports this error.

2. If OST file related with Exchange Server mailbox has gone inaccessible i.e. user is unable to access the file with MS Outlook then the error might have occurred while pursuing synchronization

In such situations, you must take necessary actions so as to resolve the issue of corruption so occurred. If you confirm that the corruption of the OST file is due to damage caused to OST file, then the best way to get your data back is by going for OST repair tool and restore it. On the other hand, if the OST file is causing troubles while synchronizing and converting into PST, then it is suggested that the user must go for ost to pst conversion.

OST to PST conversion can be eased through third party applications, known as OST to PST conversion or OST repair tools. These applications effectively convert OST file data to PST file format so that the data becomes accessible with MS Outlook. After ost to pst conversion, the resulted data can be directly imported to MS Outlook profile and can be used to access data from Exchange Server.