Index rebuilding issue Outlook Windows 11

Hi, I am an IT employee in several companies, recently I noticed that in a few users I suppose that after the Win11 update, Outlook lost the index and rebuilds it from scratch. This is a nuisance because people have a lot of emails in the archive and can't search them. Do you know a way to prevent Windows from destroying the index and rebuilding it from scratch? The issue has been dragging on for over a year

It appears it is by design when upgrading to 11 that search indexing will be rebuilt. See if this article helps. Outlook search does not return results after upgrade to Windows 11 - Microsoft Support

You can speed up the index rebuild significantly in, at least, Windows 10 by disabling Indexer Backoff. Disabling Backoff stops indexing being stopped because of user activity.
In other words, Indexing will be as rapid if users are working on their computers as it would be if they went away. I always have Backoff disabled and I've never noticed any reduction in the performance of other jobs.
Enable or Disable Indexer Backoff [its reduced speed during user activity] - TenForumsTutorials
If this would be of interest then I suggest you ask in that tutorial thread whether or not the same method applies to Windows 11.
- There is no Windows 11 tutorial but there's a long list of tutorials that he's converting over to Windows 11 and this one might merely be low down in his list.
- Certainly, the way Backoff is referred to here with a TenForums link implies that the method for disabling Backoff applies to Windows 11 as well - Reset and Rebuild Search Index - ElevenForumTutorials

Brink said:

By default, the search indexer backoff feature will reduce indexing speed while rebuilding the index when there is user activity, and will automatically continue at full speed when no user activity is detected.

Click to expand...

Best of luck,
Denis