Do you have problem in searching outlook emails then you can try and see if rebuilding the index fixes the problem. To rebuild the search index in Outlook 2016, 2013 and 2010, click the File menu followed by options link. In the Outlook Options window, navigate to Search section and click the Indexing Options button.
In the following Indexing Options window will be displayed, click the Advanced button.
In the Advanced Options, navigate to the Troubleshooting section and click the Rebuild button.
The following confirmation message would be displayed. Click the Ok button to continue with rebuilding the index.