I spent ages looking for this solution so want to share it, I had a problem with a handful of users that had access to lots of mailboxes and it was caching them and when the .ost file got to 50GB Outlook started to crash or in some cases not even open.
When configuring Microsoft Outlook 2010 or Microsoft Outlook 2013 profiles with Cached mode enabled and you add another user’s mailbox or shared folder to the profile. This means all items within the mailbox you have access to are downloaded to your local cache file.
Note: This is different from Microsoft Outlook 2007 where only non-mail items are cached by default.
If you select the shared Inbox folder for a user and the stats bar displays Connected then the mailbox is being cached.
To change the shared folder caching behaviour in Microsoft Outlook 2010 or Microsoft Outlook 2013 to match the default behaviour in Microsoft Outlook 2007, then you must add the following registry data to your Outlook client. In this situation, only non-mail folders such as Calendar, Contacts and Tasks items are cached.
HKEY_CURRENT_USER\Software Microsoft\Office\xx.0\Outlook\Cached Mode
where xx.0 is
for Outlook 2010 and
for Outlook 2013
Note: If you configure the registry value in the Policies registry key, the change is applied to all existing Outlook profiles. If you configure the registry value in the non-Policies key, the change only applies to new Outlook profiles that you create.
Use the following method to configure the registry data for Outlook 2010 and Outlook 2013:
Manual modification of the Registry
Note: This section, method, or task contains steps that tell you how to modify the registry. However, editing the registry can cause serious problems and advise that you take a backup before you start.
To change the shared folder caching behaviour in Outlook 2010 and Outlook 2013 you will need to add a registry value to your Outlook client. Follow the following instructions on adding the registry value.
- Close Outlook.
- Start Registry Editor:
- For Windows Vista and for Windows 7, click Start.
- Type regedit in the Search box and then press Enter.
- Locate and then click the following registry key:HKEY_CURRENT_USER\Software\Microsoft\Office\xx.0\Outlook\Cached Mode
Where xx.0 is 14.0 for Outlook 2010 and 15.0 for Outlook 2013.
- Note If the Cached Mode key does not exist, create this key by following these steps:
- Select the Outlook key.
- On the Edit menu, point to New, and then click Key.
- Type Cached Mode, and then press Enter.
- Select the Cached Mode key.
- On the Edit menu, point to New, and then click DWORD Value.
- Type CacheOthersMail, and then press Enter.
- On the Edit menu, click Modify.
- Type 0 (zero), and then click Ok.
- Exit Registry Editor.
- Start Outlook.