Thanks for your post. From what you described, I understand that you're having a search/indexing problem in new Outlook for Windows.
Have you already tried the steps in the Q&A Assist reply? If yes, what happened afterward? And could you please also confirm: When you search, do you get no results at all, or only partial/ recent-only results?
In addition, please try these steps:
1, Review the Search scope in new Outlook
Go to Settings > General > Search and check the search scope. Microsoft notes that if search returns no or unexpected results, adjusting the default scope (for example, using Current Folder) can improve results.
2, If you are trying to find older mail, increase the offline sync window
Go to Settings > General > Offline and increase Days of email to save.
3, If search is returning too many results, use filters
Microsoft also notes that when New Outlook finds too many matches, older items may not be shown, so using filters can help narrow the results.
4, If you expect results from Deleted Items, make sure that folder is included
In Settings > General > Search, make sure Include deleted items is enabled.
You can see this guide: Search for email in Outlook for Windows - Microsoft Support
Looking forward to your reply so I can guide you further. Thank you for your time and understanding.
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