"Something went wrong" error only when searching Shared Mailboxes

Question

My primary mailbox search works perfectly, but as soon as I click into the Shared Mailbox which has about 15GB of data, the search fails instantly.

Thank you

Answer 1

Hi Fukumioka

Based on your description, I would like to share some information from my research that I hope will be helpful.

Adjust Caching for Shared Folders.

This setting controls whether Outlook downloads a local copy of the shared mailbox.

• In Outlook, go to File > Account Settings > Account Settings... > Double-click on your primary email account.
• Click the More Settings... button, then go to the Advanced tab.
• Find the checkbox labeled "Download shared folders."
  • If it is checked: Uncheck it. Click Apply/OK > restart Outlook. This forces Outlook to use the server's more reliable online search for the shared mailbox.
  • If it is unchecked: Check it. Click Apply/OK > restart Outlook. This will begin downloading a local copy of the shared mailbox. Please note that with a 15GB mailbox, this process will take a significant amount of time, and you will see "Updating this folder" at the bottom of Outlook. Please allow it to finish completely before testing the search again.

Force Outlook to Use Its Local Search Engine

This technical step tells Outlook to stop using a newer, server-based search feature that can sometimes fail with shared mailboxes.

Note: Editing the registry can cause issues if done incorrectly. Please consider backing up your registry first.

• Close Outlook completely > Press the Windows Key + R, type regedit, and press Enter.
• Navigate to this key: HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Outlook\Search
• Right-click on the Search folder, select New > DWORD (32-bit) Value and name the new value exactly: DisableServerAssistedSearch
• Double-click it and set the Value data to 1 > Click OK, close the Registry Editor, and restart Outlook.

Rebuild the Search Index

• In Outlook, go to File > Options > Search.
• Click Indexing Options..., then click the Advanced button.
• Under the "Troubleshooting" section, click Rebuild > Click OK to confirm. This process can take several hours, but you can continue to use your computer. Search results will be incomplete until it finishes.

Temporary Workaround:

As a reliable temporary workaround, you can use Outlook on the Web. The search function there queries the server directly and should work without issue.

I hope this information helps, and I look forward to your update.

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Answer 2

The behavior matches a known issue where searching in shared mailboxes fails while the primary mailbox search works.

To resolve this for a large shared mailbox (~15 GB):

1. Make sure Outlook is fully updated to the latest build for classic Outlook for Windows.
2. If the shared mailbox is on Exchange Server 2019 or 2016 and is added as an additional account in Outlook, ensure the Exchange server is updated:
   • For Exchange Server 2019: install Cumulative Update 2 or a later cumulative update.
   • For Exchange Server 2016: install Cumulative Update 13 or a later cumulative update.
3. After updating Exchange and Outlook, restart Outlook and test search again in the shared mailbox.
4. If search still fails, repair Office from Control Panel to ensure Outlook binaries are healthy:
   • Go to Control Panel → Programs → Uninstall a program.
   • Select the Office product → Change.
   • For Click-to-Run installs, choose Online Repair and complete the wizard.
   • For MSI-based installs, choose Repair and complete the wizard.

These updates and repair steps address known problems where shared mailbox searches return no results or fail while the primary mailbox search continues to work.

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References:

• Can't search any results in manually added shared mailbox in Outlook in Exchange Server 2019 and 2016
• Troubleshooting Outlook search issues