.OST File

The ost file extension is associated with Microsoft Outlook, a personal information manager, which is part of Microsoft Office, developed by Microsoft Corporation.

The ost file stores e-mail messages and other data saved by the application from an Exchange server.

The ost files are very similar to the *.pst personal folder files, but do not support large file sizes.

The ost files are created when the "Use Offline Folders" option is checked in Outlook and are stored on the hard drive instead of the e-mail server.

Default location of ost files is:

Windows Vista, Windows 7, Windows 8, Windows 10

\Users\user\AppData\Local\Microsoft\Outlook

Windows XP or Windows Server 2003

\Documents and Settings\user\Local Settings\Application Data\Microsoft\Outlook

An ost file extension is used for Microsoft Outlook Offline Folders files. The ost files are used to store e-mail messages and other data download from an Microsoft Exchange server. Microsoft Outlook Offline Folders files are very similar to Outlook personal folders files (.pst files).

How to open:

Use Microsoft Office Outlook to open/import Microsoft Outlook inbox off-line folder files.

How to convert:

Kernel for Exchange OST Recovery can recover emails from OST files and then converts them PST format using Microsoft Exchange 5.0, 5.5, 2000 and 2003.