Outlook Shared Mailbox Search Returns No Results: Fix

You have full access to a shared mailbox in Outlook, but when you try to search for emails inside it, the search returns no results. This problem occurs because Outlook by default does not download shared mailbox items to your local cache, so the Windows Search index cannot scan them. This article explains the root cause and provides a permanent fix using Outlook account settings and the Windows Registry.

We will cover how to enable cached mode for a shared mailbox, how to reindex the mailbox, and what to do if search still fails after applying the fix. These steps work in Outlook for Microsoft 365, Outlook 2021, 2019, and 2016 on Windows 10 and Windows 11.

Why Outlook Shared Mailbox Search Returns No Results

Outlook uses the Windows Search index to find email messages, calendar items, and contacts. When you add a shared mailbox, Outlook treats it as a secondary mailbox. By default, Outlook does not download the shared mailbox contents to your local offline Outlook Data File (.ost). Without a local copy, Windows Search has nothing to index, so every search returns zero results.

This behavior is controlled by the “Download shared folders” setting in the Exchange account advanced properties. When this setting is disabled, Outlook accesses the shared mailbox items directly from the Exchange server. The server-side search in Exchange Online or on-premises Exchange does not report results back to the Outlook client in the same way a local index does. The result is an empty search pane even though the mailbox contains emails.

The Role of the Offline Outlook Data File

Every Exchange or Microsoft 365 mailbox that uses Cached Exchange Mode creates an .ost file on your computer. This file contains a synchronized copy of your mailbox data. The Windows Search indexer reads the .ost file to build its search database. A shared mailbox without the “Download shared folders” option does not create a separate .ost file. Instead, Outlook reads the data live from the server, and the indexer never sees it.

Why Rebuilding the Index Alone Does Not Help

Many users try to rebuild the Windows Search index, but this action only reindexes data that is already cached locally. If the shared mailbox is not cached, rebuilding the index has no effect. The fix must start by enabling local caching for the shared mailbox.

Steps to Enable Cached Mode for the Shared Mailbox and Rebuild the Index

1. Open Account Settings
   In Outlook, go to File > Account Settings > Account Settings. Select your Microsoft 365 or Exchange account and click Change.
2. Open More Settings
   In the Change Account window, click More Settings. Go to the Advanced tab.
3. Enable Download Shared Folders
   Under “Cached Exchange Mode Settings,” check the box labeled Download shared folders. Click OK and then Next. Finish the wizard and click Finish. Restart Outlook when prompted.
4. Wait for Synchronization
   After restart, Outlook begins downloading the shared mailbox contents to a new .ost file. This process can take several minutes to hours depending on the mailbox size. You can check the progress by looking at the status bar at the bottom of the Outlook window. It will show “Updating shared mailbox…” while the download runs.
5. Open Search Indexing Options
   In Outlook, go to File > Options > Search. Under “Sources,” click Indexing Options.
6. Modify Indexed Locations
   In the Indexing Options window, click Modify. Ensure that Microsoft Outlook is checked. If it is not, check it. Click OK.
7. Rebuild the Index
   In the Indexing Options window, click Advanced. Under “Troubleshooting,” click Rebuild. Confirm the rebuild when prompted. The indexer will delete and rebuild the search catalog. This process can take 30 minutes or more.
8. Test Search
   Once the index rebuild completes and Outlook finishes syncing, open the shared mailbox and perform a search. Type a keyword that you know exists in the shared mailbox. Results should now appear.

Alternative Method: Registry Edit for Search Folder Population

If the shared mailbox still does not return results after enabling cached mode and rebuilding the index, the search folder population may be disabled. A registry edit can force Outlook to populate search folders for shared mailboxes.

1. Close Outlook
   Make sure Outlook is not running.
2. Open Registry Editor
   Press Windows + R, type regedit, and press Enter. If prompted by User Account Control, click Yes.
3. Navigate to the Search Key
   Go to HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Outlook\Search. If the Search key does not exist, right-click the Outlook key, select New > Key, and name it Search.
4. Create the DWORD Value
   Right-click in the right pane, select New > DWORD (32-bit) Value. Name it DisableSearchFolderPopulation. Set its value to 0 and click OK.
5. Restart Outlook and Test
   Close Registry Editor, open Outlook, wait for synchronization to complete, and test the search again.

If Outlook Shared Mailbox Search Still Fails After the Main Fix

Search Only Returns Results from Your Primary Mailbox

When you type a search term, Outlook may show results from your own mailbox but not from the shared mailbox. This indicates that the shared mailbox is still not cached. Double-check that the Download shared folders checkbox is enabled. Also verify that the shared mailbox appears in the folder list. If it does not, you may need to add it again. Right-click your account name in the folder pane, choose Add shared folder, and enter the shared mailbox email address.

Outlook Crashes or Freezes When Searching the Shared Mailbox

A corrupted .ost file can cause Outlook to hang during search. To fix this, close Outlook and run the Inbox Repair Tool (SCANPST.EXE). The tool is located in the Office installation folder, typically C:\Program Files (x86)\Microsoft Office\root\Office16 or C:\Program Files\Microsoft Office\root\Office16. Run the tool against the primary .ost file. Then delete the shared mailbox .ost file, which is located in %localappdata%\Microsoft\Outlook and has a name like sharedmailboxname@domain.com.ost. Restart Outlook to force a fresh download.

Search in a Shared Mailbox Works in Outlook Web but Not in the Desktop App

Outlook on the web uses server-side search, which always works for shared mailboxes. The desktop app relies on the local index. If web search works but desktop search does not, the local cache is missing or incomplete. Follow the steps in the main fix to enable caching and rebuild the index. Also confirm that Windows Search is running. Press Windows + R, type services.msc, press Enter, find Windows Search, and ensure its status is “Running.”

Cached Exchange Mode vs Online Mode for Shared Mailboxes

Item	Cached Exchange Mode	Online Mode
Local copy of data	Creates an .ost file on the computer	No local copy, data read from server
Search method	Uses Windows Search local index	Uses Exchange server-side search
Search speed	Fast after initial sync	Slower, depends on server response
Offline access	Available when disconnected	Not available offline
Shared mailbox search	Requires “Download shared folders” enabled	Works but results may be incomplete

Now you can enable cached mode for any shared mailbox and make search return results reliably. After applying the fix, test search with a keyword you know exists in the shared mailbox. If you manage multiple shared mailboxes, repeat the account settings change for each one. For advanced users, the registry edit for DisableSearchFolderPopulation can resolve stubborn cases where search folders remain empty.