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Outlook is using an old copy of your Offline Folder File (.ost)

“Outlook is using an old copy of your Offline Folder File (.ost) Exit Outlook

and Delete the .ost file, and restart Outlook. A new file will be automatically

created the next time you initiate a send/receive.”

This message is pretty specific and gives a solution, but doesn’t tell you where the file is. You can use search, but it’s typically in a hidden folder, so that is typically challenging.

There is a simple way to find your Outlook Offline Folder File (OST) file:

  1. If this error is up on your screen, in Outlook, click “OK” to remove the error.
  2. Click the “File” tab on the ribbon (upper left corner of your screen).
  3. Click the “Account Settings” button and then select the “Account Settings” menu from the drop-down. This will bring up Outlook’s Account Settings dialog which allows you to configure Outlook’s e-mail accounts, data files, RSS Feeds, SharePoint Lists, Internet Calendars, Published Calendars, and Address Books.
  4. Click on the “Data Files” tab.
  5. Select the entry in the list of data files that has a check mark by it.
  6. Click the “Open File Location…” button to open the directory that contains this file in Windows Explorer.
  7. Exit Outlook, and delete the offending OST file.

“Outlook is using an old copy of your Offline Folder File (.ost) Exit Outlook

and Delete the .ost file, and restart Outlook. A new file will be automatically

created the next time you initiate a send/receive.”

This error does give a very specific solution to delete a specific file. An Outlook Offline Folder File contains a cached copy of a users mailbox. Outlook will rebuild this cache when in synchronizes with the mail source. Deleting an OST won’t cause any mail to be lost from the server.

The OST file does also contain any locally stored preferences, tasks, and other items that aren’t stored on the server. These will be lost.

There is one instance where deleting an Outlook Offline Folder File will data loss. If a user has copied a large of e-mail to a folder that needs to be syncronized with a server, Outlook does this syncronization in background. This is a great feature allowing a user to copy gigabytes of e-mail quickly and get back to work. However, Outlook slowly uploads this data to the server. This scenario can happen when migrating to Office 365.

If you’ve found this article helpful, please leave a comment telling what happened to get Outlook into this state. It would be nice to find some commonality so I can add preventive measure so it doesn’t happen again.

Posted on 04/8/12 at 9:37 AM | Filed under and tagged with

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