The OST file stores the entire essential information of Microsoft Outlook mailbox and allows Outlook user to retrieve that information offline even when internet connection is not available. The OST file automatically synchronize with Exchange server without interrupting the workflow when it gets connected to Internet.
But sometime corruption enters into the OST file and it disturbs the overall synchronization process and at that time Outlook user is denied to access the Outlook OST files. Most of the times Outlook users encounters an Error Message: Cannot open your default email folders, the file Outlook.ost is not an offline folder file.
In that situation the user is not able to access the Mailbox.
The error normally happens because of the two possible reasons given below:
1). The OST file is Damaged and Outlook is not able to identify it.
2). You may have used Outlook in conjunction with the Exchange Server and Exchange Server is not able to access that particular mailbox and hence showing this error message.
In Order to resolve this Error you must have to recover or convert your OST file to PST format. First of all try fixing the issue by use Scanost.exe tool. If still you are not able to resolve the issue then use MailsDaddy OST to PST Converter application and convert your file in PST format. Now import that PST file in Your Outlook application
Have a Look on the Video Given below to perform the conversion.
Hope this will help you in Resolving the Error: Cannot open your default email folders, the file Outlook.ost is not an offline folder file.