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Why Is Outlook 2024 Not Indexing PST Files After Upgrading from Office 2016 or 2019?
Outlook 2024 PST Indexing Not Working? Here Is What You Need to Know
If you upgraded to Microsoft Office 2024 and Outlook’s search function stopped finding emails in your .pst files, this guide walks you through the problem and a confirmed fix. The issue affects users who migrated from Office 2016 or 2019, particularly when .pst files are stored on network drives.
What Is Actually Happening
Outlook 2024 appears to misread the indexed status of .pst files when their paths are mapped using a drive letter (e.g., U:\Files\Outlook\Archive). The indexing engine reports a false completion — showing something like “1,908 files indexed, 0 remaining” — without ever processing the actual mailbox content. As a result, Outlook searches only an empty index, returning “No matches found” even when emails clearly exist.
This behavior does not occur consistently across all machines. Users running identical hardware and software setups have reported that the same .pst files work perfectly on one PC and fail entirely on another. The key differentiator is file location: locally stored .pst files index correctly, while those accessed through a mapped network drive do not trigger proper indexing in Outlook 2024.
Why Network Drives Are Part of This
Microsoft has long advised against storing .pst files on network paths, citing two practical risks: slow performance and potential file corruption from dropped connections. Their support documentation specifically addresses the limitations of using personal folder files over LAN and WAN links.
That said, many users have operated .pst files on network drives without incident through Outlook 2007, 2010, 2016, and 2019. The reasonable concern here is consistency — if Outlook 2024 introduced a regression that breaks network-path indexing, that represents a functional change users were not warned about. Making it more confusing, Microsoft simultaneously allows .pst files to be stored in OneDrive, which creates its own set of instability issues. The contradiction is worth noting.
The Fix That Actually Works
A user working through this problem discovered a reliable solution involving UNC path conversion. Here is the process step by step:
- Open Windows Control Panel → Mail → Show Profiles → Properties → Data Files.
- Locate the .pst file showing a mapped drive path (e.g., U:\Files\Outlook\Archive).
- Double-click the file entry, or right-click and open its Properties window, then immediately close it using Cancel or the X button.
- The path will automatically update to its full UNC equivalent: \\?\UNC\Servername\Share\…\Files\Outlook\Archive.
- Once this change takes effect, Outlook 2024 will display the correct pending count — for example, “X files still need to be indexed” — and indexing will begin.
- After indexing completes, restart Outlook. Search should now function correctly across all configured .pst files.
A notable side effect: Outlook’s startup time also improved significantly after this change, dropping from around 10 seconds to 2–3 seconds on the affected machine.
What This Tells Us
The evidence points to Outlook 2024 having difficulty resolving drive-letter-mapped paths for indexing purposes, while UNC paths work as expected. If you manage Outlook deployments across multiple users, checking how .pst file paths are registered in each profile’s data file settings is a practical first diagnostic step.
For users who transferred Outlook profiles from older Windows versions via registry export and path substitution, this path discrepancy is especially likely to appear. The registry-based path may retain the mapped drive format, which Outlook 2024 then mishandles during index verification.
If the UNC path conversion alone does not resolve the issue, also check your Windows Search indexing settings: under Indexing Options, ensure that Outlook is included in indexed locations and that the setting is configured to index file contents, not just properties.