How to rebuild outlook index?

Hi Simon Kong,

Welcome to Microsoft Q&A forum.

There is a search known issue in Legacy Outlook for Mac (v16.103.4). On macOS, Legacy Outlook uses Spotlight to index mail. If Spotlight or the local Outlook profile is not fully indexed, searches can return “No results.” Please follow these steps:

1. Rebuild macOS Spotlight (recommended)

Via System Settings (no Terminal):

• Open Apple menu > Spotlight > Search Privacy.
• Add Macintosh HD (or the Outlook data folder) to the Privacy list, then remove it to trigger re‑indexing.
• You can check progress by clicking the Spotlight icon and starting a search—macOS will show an indexing bar.

Via Terminal (quick and thorough):

• Rebuild Spotlight index for the boot volume
  • sudo mdutil -E /
• If your Mac uses APFS, rebuild the Data volume as well
  • sudosudo mdutil -E /System/Volumes/Data
• (Optional) Rebuild all mounted volumes

During re‑indexing, search may temporarily return limited results.

2. Validate Outlook’s Spotlight Importer

• Legacy Outlook integrates with Spotlight via Microsoft Outlook Spotlight Importer.
  • mdimport -L
• If you see more than one entry called Microsoft Outlook Spotlight Importer.mdimporter, keep the Outlook app you use, remove any duplicate Outlook app from Applications, Empty Trash, then restart the Mac.

Note: On newer macOS versions, some older mdimport flags are deprecated. If you see such messages, the Spotlight rebuild in step 1 (mdutil) is sufficient.

3. Confirm profile location and name

• Standard Legacy Outlook profile path:
  • ~/Library/Group Containers/UBF8T346G9.Office/Outlook/Outlook 15 Profiles/
• Open Outlook Profile Manager:
  • Finder > Applications > Microsoft Outlook > Show Package Contents > Contents > SharedSupport > Outlook Profile Manager.
• Ensure the Profile name contains no special characters (e.g., “/”). If it does, rename the profile folder accordingly.

4. (Optional) Refresh cache per folder

• In Legacy Outlook, right‑click a mail folder > Properties > Empty Cache. Outlook will reload that folder’s content from the server.

5. Validate search after rebuild

• Try a few queries:
  • subject:"invoice"
  • from:Contoso
  • hasattachment:yes

If the answer is helpful, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment".  

Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.