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OUTLOOK.OST Recovery

Posted on 1999-01-05
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Last Modified: 2012-05-07
They have moved to a new Exchange Server within my organization. Now I have an old OST file with a connection to a new Exchange Server (> 200 MB). They made no backup of my old mailbox so I need to recover the data from the *.ost file. As far as I know there´s an internal id stored in the file that represents the mailbox that was used to create the ost file. Is there any chance to open the .ost file without having a connection (or even a profile) to the old mailbox?
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Question by:apawlik
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by:dlanssens
ID: 1622451
Check this out (Ms-Technet).  Hope this answers your question.

Restoring from an .Ost File After Mailbox Deletion
Ost files are “slave” replicas of Microsoft Exchange Server folders. If you delete the master, the slave is orphaned. If the original Microsoft Exchange profile was not modified, then you can start the process offline with the old .ost file, and recover the data by copying it to a .pst file. However, if the old profile was deleted or modified (for example, if you used the profile to log on to the new mailbox), the data is lost.
The reason data is lost is due to the way in which security is enforced on .ost files. You cannot perform Windows NT authentication while you’re offline. Instead, you have to prove that you can log on to the server-based master before the .ost file will give you local access.
Microsoft Exchange Server does this by creating an encrypted “cookie” from your mailbox’s unique entry ID, while you have successfully logged on to the server. This cookie is securely stored in your Microsoft Exchange Server profile. Your profile stores the key for the .ost file. Every time you try to access the .ost file, it checks your profile for the existence of this key.
The exception to making the .ost file non-recoverable occurs if one of the following takes place:
·      You delete the master server mailbox.
·      You also delete or modify the profile containing the key to the .ost file.

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It is possible to recover mail stored in an OST provided you have not tried
to modify the profile that was used to create the OST file. If the profile
used to create the OST file has been modified to point to a new mailbox,
the information contained in the OST file may be lost.
 
The reason for this is due to how security on an OST works because Windows
NT authentication cannot be used when working offline. Therefore, you must
"prove" that you're allowed to log onto the server-based master before the
OST file will give you local access. Microsoft Exchange does this by
creating an encrypted "cookie" from your mailbox's unique entry ID while
you are successfully logged into the Microsoft Exchange Server. This cookie
is securely stored in your Microsoft Exchange profile. Essentially, your
profile stores this key for the OST. Every time you try to access the OST
file it checks your profile for the existence of this key.
 
By modifying the profile or trying to connect to a new mailbox or new
server with the current profile, Microsoft Exchange replaces this key with
a new value from the mailbox that was created. At this point, there is no
method to get into the data that was contained in the OST created against
the first mailbox.

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Steps to recover
================
 
If you have not modified your profile or attempted to log in online to the new
mailbox, use the following steps to copy the offline messages into a PST.
 
1. Start the Microsoft Exchange client up OFFLINE.
2. Click Services from the Tools menu.
3. Click Add.
4. Add a Personal Folders (PST) service.
5. Highlight messages to be copied.
6. Click Copy from the File menu.
7. In the Copy to: dialog box, select the Personal Folders (PST) created in
   step 4.
8. Click OK.
9. Repeat steps 5 - 8 for each folder containing messages.
 
At this point, the messages are copied to a PST. A new profile can be
created and you can login to the new server based mailbox. Once this
is completed successfully, a Personal Folders service can be added
(referencing the PST created above), the messages can be copied from the
PST back to the server based mailbox.

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Author Comment

by:apawlik
ID: 1622452
That´s the same information I received after hours of "surfing" around. I don´t have the old exchange server settings and I think there must be a way to restore the OST file - even when there´s no server authentication available.
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Expert Comment

by:david_levine
ID: 1622453
I found a bunch of hits on DejaNews which say to run Outlook in Offline mode and you should be able to open the OST file. Did you try that? If so, does it give you an error?

Check out the following Microsoft KB Articles...
http://support.microsoft.com/support/kb/articles/q183/0/52.asp
http://support.microsoft.com/support/kb/articles/q163/5/89.asp
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Accepted Solution

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reddarin earned 180 total points
ID: 1622454
Unless you have a tape backup of the workstation prior to the change, there is no way to recover the OST. MS goes to court quite a bit over that issue.

Darin
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