How to Fix Outlook Error 0x80040600

When Outlook is unable to load, send, or receive emails, you may encounter the error: “Sending and receiving reported error (0x80040600): Unknown Error 0x80040600”. This error typically indicates that your Outlook database file (.pst or .ost) is corrupted.

This guide covers the root causes of this corruption and provides step-by-step instructions for repairing your data files on both Windows and macOS using terminal commands, PowerShell scripts, and built-in repair tools.

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1. Understand the Cause of Outlook Error 0x80040600

Error 0x80040600 represents a MAPI storage corruption error (MAPI_E_CORRUPT_STORE). This occurs when Outlook cannot parse the binary index structure of your mail database. The most common triggers are:

• Oversized Data Files: The .pst or .ost file has exceeded its size limit (usually 20 GB on older versions, or 50 GB on modern Outlook clients).
• Abrupt Shutdowns: Outlook or the OS terminated unexpectedly (due to a power failure or crash) while the database was writing cache.
• Antivirus Interference: Security software locked the file to scan it, corrupting the file headers during transmission.
• Bad Storage Sectors: Physical or logical drive degradation corrupted the specific sectors holding the file.

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2. Windows: Locate and Repair PST/OST Files

To resolve this on Windows, you must locate the corrupt file and use Microsoft’s built-in Inbox Repair Tool (scanpst.exe).

Step 1: Force Close Outlook

Ensure no background processes are locking the databases:

taskkill /F /IM outlook.exe

Step 2: Locate your OST or PST File

By default, files are stored in the following paths:

• OST (Exchange/IMAP): %localappdata%\Microsoft\Outlook\
• PST (POP3/Archives): %userprofile%\Documents\Outlook Files\ or %localappdata%\Microsoft\Outlook\

You can verify the location by opening the Control Panel → Mail → Data Files.

Step 3: Run the Inbox Repair Tool (scanpst.exe)

If it is an .ost file (Exchange/Office 365), you can safely delete it, and Outlook will rebuild it:

del /q /f "%localappdata%\Microsoft\Outlook\*.ost"

If it is a .pst file (POP3, containing local folders not stored on the server), do not delete it. You must repair it:

1. Find scanpst.exe in your Office directory (e.g. C:\Program Files\Microsoft Office\root\Office16\scanpst.exe).
2. Run the tool.
3. Browse to select your corrupted .pst file.
4. Click Start to scan, check “Make backup of scanned file before repairing”, and click Repair.

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3. macOS: Reset SQLite Profiles

On macOS, Outlook does not use .pst or .ost files for database management; instead, it relies on a SQLite structure.

Reset the Active Outlook Profile Cache

If Mac Outlook experiences synchronization failures or database corruption:

# Force quit Outlook and database services
killall "Microsoft Outlook"
killall "Microsoft Outlook Registration Database Daemon"

# Create a backup of the profile folder before clearing
cp -R ~/Library/Group\ Containers/UBF8T346G9.Office/Outlook/Outlook\ 15\ Profiles/Main\ Profile ~/Library/Group\ Containers/UBF8T346G9.Office/Outlook/Outlook_Backup

# Clear the cached profile files
rm -rf ~/Library/Group\ Containers/UBF8T346G9.Office/Outlook/Outlook\ 15\ Profiles/Main\ Profile/Data/Caches/*

Note: If the profile is completely corrupted, launch the Outlook Profile Manager (/Applications/Microsoft Outlook.app/Contents/SharedSupport/Outlook Profile Manager.app/Contents/MacOS/Outlook Profile Manager) and create a new default profile.

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4. Automated Script to Locate the Inbox Repair Tool

If you cannot locate the scanpst.exe tool manually on Windows, copy and run this PowerShell script to search common directories and launch it:

# Run in PowerShell to locate and launch scanpst.exe
$scanpstPaths = @(
    "C:\Program Files\Microsoft Office\root\Office16\scanpst.exe",
    "C:\Program Files (x86)\Microsoft Office\root\Office16\scanpst.exe",
    "C:\Program Files\Microsoft Office\Office16\scanpst.exe",
    "C:\Program Files (x86)\Microsoft Office\Office16\scanpst.exe",
    "C:\Program Files\Microsoft Office\Office15\scanpst.exe"
)
$found = $false
foreach ($path in $scanpstPaths) {
    if (Test-Path $path) {
        Write-Host "Success: Found Inbox Repair Tool at: $path" -ForegroundColor Green
        Start-Process -FilePath $path
        $found = $true
        break
    }
}
if (-not $found) {
    Write-Warning "scanpst.exe could not be found. Please check your Office installation."
}

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5. Summary Diagnostics Checklist

Diagnostics Step	Action / Path	Expected Outcome
Verify Storage Space	Check local drive capacity	Ensures there is enough disk space to write and expand repair logs.
Run scanpst.exe (Win)	Select your .pst file in the Inbox Repair Tool	Scans and repairs internal block structures and index values.
Delete OST Cache (Win)	Remove .ost files from %localappdata%\Microsoft\Outlook	Outlook auto-rebuilds a healthy mail cache from the server.
Reset Cache (Mac)	Delete files inside .../Outlook 15 Profiles/.../Caches/	Clears sync locks and forces database validation.
Create New Profile	Control Panel (Win) or Profile Manager (Mac)	Creates a fresh, clean database structure from scratch.