Hi,
What is the specific build number of Outlook you are using?
Which type of email account do you use? Exchange, IMAP or POP3? There is a known issue for some users after updating to 16.0.9001.2171 and later versions that Outlook search returns no search results for POP and IMAP accounts. See No
search results for POP/IMAP accounts and check whether it matches your situation.
Besides, you may also try follow the general troubleshooting steps to troubleshoot the search issue in Outlook:
Outlook search returns No matches found
Hope this helps.
Regards,
Steve Fan
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