Hi Roger,
Factors that could lead to Outlook search issues are various, so supposing you are experiencing any search problems, would you please elaborate it a bit more so that we can help you better? For instance, you may share more information like the Outlook version, the issue symptom, whether it's only affecting particular users, if the issue can be reproduced in OWA?
In addition, here is an official article about the most commonly used troubleshooting methods and possible solutions when dealing with Outlook search issues, hopefully you can find it helpful:
Troubleshooting Outlook search issues
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