Fix: Outlook Search Not Finding All Emails

We recently helped a customer who was struggling with Outlook search returning incomplete results. When searching for emails from specific contacts, only one result would appear when there should have been 20 or more. Other staff members could see the full email history with the same contacts without any issues. After weeks of troubleshooting, including checking mailbox settings and escalating to Microsoft, the fix turned out to be a simple toggle in Exchange Admin Center that reset the search indexing.

Symptoms

Users may experience one or more of the following issues with Outlook search:

• Searching for a contact returns only one or two emails when there should be many more
• Outlook search returns no results at all for known emails
• Search works correctly for other users in the same organisation but fails for one specific mailbox
• Recently received emails do not appear in search results

“Outlook search is only showing 1 email from [contact] but I know there are at least 20 conversations.”

Cause

This issue occurs when the Outlook Web Access (OWA) settings on the user’s Exchange Online account become misconfigured. The OWA mailbox policy controls how the mailbox interacts with search indexing. When this policy enters a broken state, Outlook desktop search relies on a corrupted or incomplete index, resulting in missing search results.

This can happen after mailbox migrations, licence changes, or policy updates in Microsoft 365.

Resolution

Follow these steps to resolve incomplete Outlook search results.

Step 1: Disable and Re-enable Outlook Web Access

1. Sign in to the Exchange Admin Center
2. Navigate to Recipients > Mailboxes
3. Select the affected user’s mailbox
4. Click Manage email apps settings (under Mailbox)
5. Turn off Outlook on the web
6. Click Save
7. Wait 5 minutes, then return to the same setting and turn Outlook on the web back on
8. Click Save

This resets the OWA access policy and triggers a re-index of the mailbox for search.

Step 2: Rebuild the Outlook Search Index Locally

After resetting OWA, rebuild the local search index on the affected device:

1. Open Outlook on the user’s computer
2. Go to File > Options > Search
3. Click Indexing Options
4. Click Advanced
5. Under Troubleshooting, click Rebuild
6. Click OK and allow the indexing to complete (this may take 15-30 minutes depending on mailbox size)

Step 3: Check Cached Exchange Mode Settings

Ensure Cached Exchange Mode is configured correctly:

1. In Outlook, go to File > Account Settings > Account Settings
2. Select the Exchange account and click Change
3. Confirm that Use Cached Exchange Mode is ticked
4. Set the slider to All to download the full mailbox (or at least 12 months)
5. Click Next > Done and restart Outlook

Workaround: Use Advanced Search

While waiting for the index to rebuild, users can use Outlook’s Advanced Search as a temporary workaround:

1. In Outlook, press Ctrl + Shift + F to open Advanced Find
2. Set the From field to the contact you are searching for
3. Ensure Look in is set to the correct mailbox folder (or all folders)
4. Click Find Now

Important Notes

• Disabling OWA temporarily prevents the user from accessing their email via the web. Coordinate with the user before making this change.
• The search index rebuild can take some time for large mailboxes. Let the user know search results may be incomplete for 15-30 minutes after the rebuild starts.
• If the issue persists after these steps, check whether a mailbox migration or licence change occurred recently, as these can sometimes cause the OWA policy to break again.

Related Resources

• Fix: Legitimate Emails Going to Junk in Outlook
• How to set up a signature in Outlook
• How to delete an Outlook Group
• Microsoft: Find a message or item with Instant Search
• Microsoft: Manage user mailboxes in Exchange Online
• Microsoft: Fix search issues in Outlook

If you need help with Outlook search or email issues, get in touch with our team.