Hi,
To troubleshoot the issue, please first make sure indexing is complete. To verify this, please follow:
- In Outlook, click in the Search box.
- Click the Search tab, click Search Tools, and then click
Indexing Status.
- When the Indexing Status dialog appears, you should see the following:
Outlook has finished indexing all of your items.
0 items remaining to be indexed.
If Outlook has not finished indexing all of your items, note the items remaining to be indexed, wait 5 minutes, and then check again. If the number of items did not decrease, continue to troubleshoot by using the steps in the following KB article:
https://support.microsoft.com/en-us/kb/2769651
Hope this helps.
Regards,
Steve Fan
TechNet Community Support