When indexing in Microsoft Outlook never completes and keeps restarting on every session, there may be a problem with the indexing service or the Outlook data file may be corrupted. There are a few things to do to troubleshoot and find out where the problem is.

One of the first things to do is to enable logging of indexing results:

  1. Registry Location: HKCU\Software\Microsoft\Office\xx.0\Outlook\Search where xx is the Microsoft Office version.
  2. DWORD Key: EnableLogging
  3. Value: 0xffff0000
  4. Log File Location: %TEMP%\outlook logging
  5. Check Event Viewer for Error ID 29 to 37.
  6. Review settings in “Indexing Options”. You can search this application using the Windows Desktop Search function.
[Microsoft Support] Outlook search returns No matches found.