.OST File Extension

Microsoft Exchange/Outlook Offline File

Question: What is an OST File?

Have you found, downloaded or received an OST file, but don't know which software program is required to open it?

Before attempting to open an OST file, you'll need to determine what kind of file you are dealing with and whether it is even possible to open or view the file format.

Answer: Files which are given the .OST extension are known as Microsoft Exchange/Outlook Offline files, however other file types may also use this extension. If you are aware of any additional file formats that use the OST extension, please let us know.

How to open a OST file:

The best way to open an OST file is to simply double-click it and let the default assoisated application open the file. If you are unable to open the file this way, it may be because you do not have the correct application associated with the extension to view or edit the OST file.

This file format was added to our database by a visitor to this site, but no additional information was provided. We have yet to investigate this file type further, or there was not enough information available at the time to report accurately on the format.

Please check back soon for more information as we are constantly updating our file descriptions based on search frequency.

Tip: Try to open the OST file using a text-editor such as Notepad, as many file types contain simply contain unformatted plain-text and can viewed correctly using this method.

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Comments (2)
showing 1-2
Anand Jamkhandi
2011-03-26 03:12:52
While configuring the mail account under Microsoft Exchange, I am getting an error 'Cannot open your default e-mail folders. You must connect to Microsoft Exchange with current profile before you can synchronize your folder with your Outlook data file (.ost).

What could be the error? I am following correct procedure.
2015-02-02 12:36:19
OST file is an offline storage table (.ost) file which is created by MS Outlook.