Resolving Error '.ost is not an offline folder file.' after Deleting the Exchange Account

Published: 10th February 2010
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Outlook Offline Folder (.ost file) facilitates offline data access when using an Exchange Server account. To continue using the file, user requires not to delete or modify the Exchange profile or otherwise, the file will be left as orphaned. . The reason is that this profile contains some valuable information required to access the mailbox on server. An orphaned or unusable OST however, can be converted to PST using a Convert OST to PST tool.

The following scenario depicts the similar type of problem with an Outlook offline folder.

1)You use Microsoft Office Outlook with an Exchange corporate account

2)Then, you create a POP3 e-mail account and define it as default

3)Next, you delete the Exchange corporate account

4)When you try to access e-mails stored in OST of earlier Exchange account to import in the new account, you cannot do so and receive an error, similar to below:

"Cannot open your default email folders. The file file_pathfile_name.ost is not an offline folder file."

As a result of this error message, you cannot access the e-mails stored in the OST file.


The Exchange Server account consists an identification key that Outlook client requires to authenticate to log on to the Exchange mailbox. In this case, this key has been deleted and as a result, Outlook cannot synchronize with the mailbox and allow you to access the data.

The same error also occurs if the OST file is corrupted and thus Outlook cannot recognize it.


The error, stated above, includes the OST file path that can help you to locate the file. On locating the file, you can perform any of the suitable steps:

1)Rename or delete the affected OST and create a new profile that will generate a new OST also. This method is suggested only when you have a backup of your e-mails

2)Try repairing the corrupted OST with the OST integrity checker tool (Scanost.exe)

3)Convert the unusable and/or corrupted OST to application-usable PST. This is feasible using a Convert OST to PST utility. The third-party Convert OST PST software are powerful and safe utilities that come with an easy-to-use interface.

Stellar Phoenix Mailbox Exchange Desktop is a reliable utility that converts an unusable OST to Outlook-importable PST. The Convert OST to PST utility supports MS Outlook 2007, 2003, 2002, and 2000. With an interactive display, the software is easily operable without any prior technical skills. The tool is compatible with Windows 7, Vista, XP, 2003, and 2000.

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