Outlook shared mailbox search not working: how to fix it

Find your symptom

What you see	Likely cause	Fix
No shared mailbox results with All Mailboxes	Design limitation	Search Current Folder, or add the mailbox as an account
Only recent shared emails are found	Cached copy is limited	Set the offline slider to All
Nothing found, even in your own mailbox	Search index problem	Check and rebuild the index
Results don’t update, clicking one gives an error	Known issue (Sept 2026)	Turn off server-assisted search
Problem is in new Outlook	Search works per folder	Select a shared folder first

Search the right scope

Microsoft’s Outlook search troubleshooting page says that All Mailboxes and All Outlook Items return limited or no results from shared and archive mailboxes, and that this “will not change”. So:

1. Click a folder in the shared mailbox, such as its Inbox.
2. Click in the search box at the top.
3. Set the scope drop-down next to the box to Current Folder (or Subfolders if you need the folders below it).
4. Type your search.

Add the shared mailbox as its own account

Microsoft also suggests adding the shared mailbox as a separate account rather than relying on the automatic entry. Our guide to adding a shared mailbox covers the full steps. In short:

1. If you added the mailbox yourself, remove it from File > Account Settings > Account Settings, select your account, then Change > More Settings > Advanced and remove it under Open these additional mailboxes.
2. Go to File > Add Account and enter the shared mailbox address.
3. When asked for a password, choose Sign in with another account and use your own work account.
4. Restart Outlook and search again.

A mailbox added automatically by your admin (automapping) comes back if you remove it, so ask IT to turn automapping off for you first.

Old emails missing from results

According to Microsoft Learn, when Cached Exchange Mode and Download shared folders are on (the default), the Mail to keep offline setting also applies to shared mailboxes. Search then returns only the emails cached on your PC, with no link to search the server for more.

1. Go to File > Account Settings > Account Settings, select your account and click Change.
2. Move the Mail to keep offline slider to All.
3. Click Next, then Done, and restart Outlook. Give it time to download the older mail.

If you want a smaller cache for your own mailbox but everything for shared ones, Microsoft documents a registry value that removes the limit for shared mailboxes only. Back up the registry first and create this value with Registry Editor:

HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Outlook\Cached Mode
DWORD (32-bit): DisableSyncSliderForSharedMailbox
Value: 1

Results don’t update or show errors (2026 known issue)

Microsoft lists this as a classic Outlook known issue for Outlook for Microsoft 365, marked fix in progress on September 29, 2026, with no date for the fix. Server-assisted search results don’t refresh when items change. An email you move stays in the results, and clicking it gives an error. The same can happen after you change categories or mark items read or unread. Microsoft hasn’t said which builds are affected.

Microsoft’s workaround is to turn off server-assisted search so Outlook falls back to Windows Desktop Search (the local index):

1. Close Outlook and open Registry Editor (regedit).
2. Go to the key below. Create the Search key, and any missing ones above it, if it doesn’t exist.
3. Create a DWORD (32-bit) Value named DisableServerAssistedSearch and set it to 1.
4. Start Outlook again.

HKEY_CURRENT_USER\Software\Policies\Microsoft\Office\16.0\Outlook\Search
DWORD (32-bit): DisableServerAssistedSearch
Value: 1

Two things to know. Results now come from your local index, so emails that aren’t cached may not appear (we’re inferring this from Microsoft’s description). And Microsoft doesn’t give undo steps, but once the fix arrives, deleting the value should restore normal search. On a work PC, check with IT before you edit a Policies key.

Fix the local search index

If search finds nothing anywhere, even in your own mailbox, the Windows index is the problem. Microsoft’s troubleshooting page suggests:

• In Outlook, click in the search box, open Search Tools and check Indexing Status. Leave Outlook open until it finishes.
• In Search Tools > Locations to Search, make sure every mailbox is ticked.
• Open services.msc and make sure Windows Search is running and set to Automatic (Delayed Start).
• In Control Panel, open Indexing Options, check that Microsoft Outlook is listed, then use Advanced > Rebuild.

If that doesn’t help, try a new Outlook profile; see how to reset Outlook to default settings.

New Outlook

New Outlook shows shared mailboxes under Shared with me. Select a folder there before you search, because results come from the selected folder. New Outlook can’t search several accounts at once, so search each one separately. You can set the default scope under Settings > General > Search. The registry workaround above is for classic Outlook only. If you want classic Outlook back, see how to get classic Outlook.

Still stuck? Search the shared mailbox in Outlook on the web, which doesn’t use your PC’s index. If emails also refuse to move between folders, see can’t move emails to folders in Outlook.

Related guides

• How to Add a Shared Mailbox in Outlook (Windows, Mac, Web and Mobile)
• How to reset Outlook to default settings (classic and new Outlook)
• Can’t move emails to folders in Outlook: how to fix it
• Classic Outlook download: how to get it back on Windows 11 and 10

Official sources

• Microsoft: Classic Outlook issues with service assisted search for shared mailboxes
• Microsoft: Troubleshooting Outlook search issues
• Microsoft Learn: Only a subset of items are synchronized in shared mailboxes