Based of Outlook for Office 365


Check is Shared Mailboxes are enabled to Download.

  1. Click on File.
  2. Click on Account Settings to access the drop down. 
  3. Click on Account Name and Sync Settings. 
  4. In the next window, click on More Settings
  5. In the next window, click on the Advanced tab. 
  6. In the next window, check inside the section Cached Exchange Mode Setting
  7. If the box, Download shared folders is checked, then any shared mailboxes that are inside Outlook will download the full contents to your PC and will take up hard drive space.

Download Shared Folders may be enabled when low bandwidth is a problem, and the online version can take a while to update when you click on it.

Disable Cached Shared Mailboxes

If you are low on Drive Space, disable.

  1. Using the instructions above, get the the Cached Exchange Mode.
  2. Uncheck the option Download shared Folders.
  3. Click on OK.
  4. You may receive a notification that you will need to close Outlook and Reopen.
  5. Close all Outlook windows and relaunch Outlook.
  6. The Shared folders should still be visible but will not load the emails as and when you open and access that shared mailbox.
  7. Leave for a couple of days before requesting that the OST files are removed.