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Outlook Cached Exchange Mode

Outlook Cached Exchange Mode

Your Microsoft Outlook data is always available to you, even if you work offline.

When a connection from your computer to the server running Exchange disconnects, Microsoft Office Outlook automatically switches to Trying to connect or Disconnected. Once the connection is restored, Outlook automatically switches back to Connected. Any changes made while there is no connection will automatically synchronize once reconnected. 

Microsoft Office 2013

When an Outlook 2013 account is configured to use Cached Exchange Mode, there’s always a local copy of the user’s mailbox available as an offline data file (.ost file) on their computer. This is by default in 
C:\Users\<username>\AppData\Local\Microsoft\Outlook folder.

When Outlook 2013 is installed, a new compressed version of the .ost file is created by default.


Configure Cache Exchange Mode settings

The Sync Slider in the Outlook 2013 Server Settings dialog box allows you to specify the time frame to keep mail offline.

  1. In Outlook click File > Accounts Settings > Accounts Settings.
  2. Select the account you want to configure in the Name column and click Modify.
  3. In the Exchange Settings dialog box, select the Cached Exchange Mode check box.
    3. Move the slider to the timeframe that you want your Mail to keep offline.
  4. Click More Settings > Advanced and clear the Download shared non-mail folders check box. This applies to delegated inboxes and shared calendars.

Shared mail and non-mail folders are automatically downloaded in Outlook 2013, which increases the size of users' .ost files. By selecting the Download shared non-mail folders option both mail and non-mail shared folders will be downloaded. Should you prefer not to download shared mail folders, then follow steps 1-4 listed above, and clear the Download shared folders check box. 

Change by Adding a registry key

a. Registry key: 
b. HKEY_Current_User\Software\Microsoft\Office\15.0\Outlook\Cached Mode
c. Value: CacheOthersMail = 0