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An OST file (.ost) is an offline folder file
in Microsoft Outlook. Offline folders make it possible for the user to work
offline and then to synchronize changes with the Exchange server the next time
they connect. The ability to work offline is useful in environments with
limited or unreliable connectivity.
When Outlook is used in conjunction with
Microsoft Exchange Server, you can set it to work with the Exchange mailbox
offline. At that time, Outlook will make an exact copy of your mailbox on the
Exchange Server, called offline folders, and store it in a local file, which is
called offline folder file and has a .ost file extension. OST is the
abbreviation for "Offline Storage Table".
When working offline, you can do everything
with the offline folders just as if it were the mailbox on the server. For
example, you can send emails which are actually put in the offline Outbox, you
can also receive new messages from the other online mailboxes, and you can make
changes to the emails and other items as you want.
However, all these changes will not be
reflected to your mailbox on the Exchange server until you connect to the
network again and synchronize the offline folders with the server.
During the synchronization process, Outlook
will connect to the Exchange server via network, copy all the changes made so
that the offline folders will be identical to the mailbox again. You can select
to synchronize only a specific folder, a group of folders, or all the folders.
A log file will be used to record all the important information about the
synchronization, for your reference later.
Since Outlook 2003, Microsoft introduces a
Cached Exchange Mode, which is actually an improved version of original offline
folders. It is featured in more efficient synchronization mechanisms and more
convenient offline operations.
Offline
folders or Cached Exchange Mode has several advantages:
Make it possible for you to work with your
Exchange mailbox even there are no network connections available.
When disaster happens on the Exchange
server, such as server crashes, server database corruption, etc., the offline
folder file on the local computer still contain a copy of your Exchange
mailbox, with some offline updates. At that time, you can utilize Advanced
Exchange Recovery to recover most of the contents in your Exchange mailbox by
scanning and processing the data in local offline folder file.
The offline folder (.ost) file, like Outlook
personal folders (.pst) file, is normally located in a predefined folder.
For
Windows NT, 2000, XP and 2003 server, the folder is:
C:\Documents
and Settings\\Local Settings\Application
Data\Microsoft\Outlook
You may also search for file
"*.ost" in your local computer to find the location of the file.
The OST file is the local copy of your
Exchange mailbox, which contains all your most important personal communication
data and information, including emails, folders, posts, appointments, meeting
requests, contacts, distribution lists, tasks, task requests, journals, notes,
etc.
When
you have various problems with your mailbox or offline folders, for example,
the Exchange server crashes or you cannot synchronize the offline updates with
the server, we highly recommend you to use Advanced Exchange Recovery to
recover all data in it.
