OST Synchronization Error : “.ost cannot be accessed”

Published: 16th September 2009
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In Microsoft Outlook, an offline folder (.ost file) is a locally stored file that is synchronized with your mailbox contents stored on Microsoft Exchange Server. The folders empower you to access them even when the mail delivery or network service is not available. The file converts into a usable .pst file as the synchronization process succeeds. But there can be several synchronization errors, due to which your .ost file might become unusable. In such cases, you might need to restore its contents from a backup stored as a .pst file. If it is not feasible, you should use a third-party tool to Convert OST to PST.

For an instance, you use Microsoft Outlook 2002 or 2003 with an offline folder. You press F9 to synchronize your .ost file with your Exchange Server mailbox, but fail to do so and come across the below error message:

"The file .ost cannot be accessed because it has been configured for use with a different mailbox."

If you close the application and try to perform synchronization again, you receive the same error message.


As the error message suggests, this error is encountered if you are attempting to synchronize the mailbox with an .ost file that is configured to use a different server or e-mail account. This usually occurs if you perform these steps in order:

1-You synchronize your .ost file with the mailbox

2-You perform some changes in name of either e-mail server or mailbox in your email account profile

Doing so makes the current .ost file unusable.


Create a new email profile with the desired account settings and restore data using any of the below solution:

1-You can then include the .pst files maintained as a backup of previous .ost file.

2-You can also copy this information to a .pst file from your mailbox after changing the changed email settings back to the original state.

3-If applying the above solutions are not possible, Convert OST to a usable .pst file.

Convert OST to PST are powerful applications that are competent to convert an usable .ost file into a usable .pst file after any type of crash.

Stellar Phoenix Mailbox Exchange Desktop is an effective utility that converts an .ost file into a .pst file. It can Convert OST by maintaining data integrity. Designed to perform safe file conversion, this utility can restore all file objects including emails, notes, journals, tasks and more. It is compatible with Outlook 2003, 2002, 2000, 98 and 97.

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