Though offline folder files or OST files in Outlook allow a user to continue working even while offline, any damage or corruption to these files could result in inaccessibility of important mails and other items. The only way to resolve standard Outlook OST file errors might be to convert OST to PST.

Microsoft Exchange Server and Microsoft Outlook are two of the most popular applications that are used in any business organization today and since they integrate well with other Microsoft enterprise level solutions, they can create a great collaborative environment at any workplace. Microsoft Exchange Server is the central repository where all the user mailboxes and the mails are stored in a well-organized database file, called as the EDB (Exchange Database) file. For every user, the organization can create a separate profile and assign a mailbox that is typically stored on the server and can be accessed by Microsoft Outlook. However, Outlook also allows the contents of the mailbox to be cached locally in the form of offline folder files. The user can work on these without being logged on to the server – this allows greater efficiency since there are no interruptions brought about by network or connection failure. On the other hand, any damage to the OST files or any accidental deletion of the mailbox from the server may render the contents of the OST file completely inaccessible. In such a situation, OST to PST conversion emerges as a good solution to restore the data.

Some standard error messages that an Outlook user might receive while working on OST files are as follows – ‘Cannot open default email folders. The file your_file.ost is not an offline folder file.’ Here, your_file.ost is the name of the offline storage file that has been created by Outlook to be the exact local copy of the mailbox stored on Microsoft Exchange server. This file is typically synchronized with the mailbox on the server so that both copes have the same content. When this error message is seen, it might mean that there is some damage or corruption in the OST file. If you have been taking regular backups of the contents in the file, it should be possible to create a new OST file, associate it with the mailbox and restore all the contents from the backup. If there are no backups or the backups are also inaccessible, the only option might be to convert OST to PST data.

Another scenario commonly faced by Outlook users is when the mailbox associated with the OST files is accidentally removed or deleted from the server. An employee who is leaving the organization could delete the mailbox without first transferring the contents of the file. Else, a network administrator fearing a security threat to the network might delete the mailbox. The only way an OST file can be accessed is when it is associated with a mailbox on the Exchange server. With no mailbox linked to the OST files, they become orphaned and the data contained in them becomes inaccessible. In these cases too, converting OST to PST seems to be the only way of recovering important data.

Converting OST to PST is not as easy as it sounds and though there are different ways of conversion, one of the simplest and quickest ways of restoring data from orphaned or damaged OST files is to use a tool such as Advanced Exchange Recovery. Advanced Exchange Recovery will save all the restored data in PST files that can be easily read by Outlook and other email clients.