Policy
Enable indexing uncached Exchange folders
Enabling this policy allows indexing of mail items on a Microsoft Exchange server when Microsoft Outlook is not running in cached mode. The default behavior for search is to not index uncached Exchange folders. Disabling this policy will block any indexing of uncached Exchange folders. Delegate mailboxes are managed separately from online mailboxes. The "Enable Indexing of Uncached Exchange Folders" has no effect on delegate mailboxes. To stop indexing of online and delegate mailboxes you must disable both policies.
40624e375226 PreventIndexingUncachedExchangeFolders Registry
Copy registry mappings
HKLM\SOFTWARE\Policies\Microsoft\Windows\Windows Search\PreventIndexingUncachedExchangeFolders (enabled) = 0
HKLM\SOFTWARE\Policies\Microsoft\Windows\Windows Search\PreventIndexingUncachedExchangeFolders (disabled) = 1 Policy notes
Enabling this policy allows indexing of mail items on a Microsoft Exchange server when Microsoft Outlook is not running in cached mode. The default behavior for search is to not index uncached Exchange folders. Disabling this policy will block any indexing of uncached Exchange folders. Delegate mailboxes are managed separately from online mailboxes. The "Enable Indexing of Uncached Exchange Folders" has no effect on delegate mailboxes. To stop indexing of online and delegate mailboxes you must disable both policies.