No doubt, Outlook is a very efficient e-mail client and personal information manager. But, some times it may show some error messages that halt your work. Consider a practical scenario where in you want to connect/access some OST file with Outlook. But it fails with the below error messages:
Unable to open your default e-mail folders. The file C:\Documents and Settings\%UserName%\Local Settings\Application Data\Microsoft\Outlook\outlook.ost cannot be accessed. You must connect to your Microsoft Exchange Server computer at least once before you can use your offlline folder file.
This situation arises when you try to access some OST file for which Exchange Server account is not available or the Outlook profile that created the OST file is being altered.
If you had altered the Outlook profile you can resolve the error by recreating the OST file.
Steps to recreate OST file.
- Quit Outlook and all mail enabled applications.
- Rename old OST file for back-up.
- Open Outlook and connect it with the Exchange Server.
New OST file will be created automatically.
But, in case the Exchange Server account is not available for the OST file (this may happen in case where in you had left your job and have no rights to access Exchange Server mailbox). You need to convert OST file to PST file to access its contents. There will be two cases and you can recover OST file accordingly.
Case1: You have access to the system on which you were accessing your mails and the Outlook profile that created the OST file is not being altered.
You can Export the OST file to PST file using Import/Export function from File menu of Outlook by opening Outlook in off-line mode.
You can also try system restore. Go back a few days and restore OST to PST file.
Case2: If you can not access the system on which the Outlook profile for the OST file is available and you only have the OST file along with you.
In this case you need to perform manual OST PST conversion for which you need to use third party convert .ost to .pst tool. After successfully converting .ost to .pst file, import the resulting PST file in Outlook.