Summary

This guide helps you troubleshoot and resolve: Archiving Old Emails in Outlook. Follow the steps below to fix the issue.

Common Causes

Prerequisites

• Sufficient disk space for the archive file.
• Outlook desktop (recommended for AutoArchive and manual exports). See How to add an email account to Outlook for installation guidance.
• Do not store PST files in OneDrive, SharePoint or any cloud-synced folder – this can cause corruption.

Method 1: AutoArchive (Automatic)

1. Configure AutoArchive settings

• Go to File > Options > Advanced.
• Scroll to the Archive section.
• Click AutoArchive Settings….

2. Set archiving rules

• Run AutoArchive every [X] days – set the frequency (e.g., 14 days).
• Show archive summary before deleting – check to review what will be moved.
• Default archive file – note the path (usually C:\Users\<user>\Documents\Outlook Files\archive.pst). You can change the location if needed.
• During AutoArchive
  • Move old items to – default action.
  • Permanently delete old items – use with caution.
  • Archive items older than – set the timeframe (e.g., 6 months).
  • Include items with “Do not AutoArchive” checked – usually unchecked.

3. Configure archive policy per folder (optional)

• Right-click a folder (e.g., Inbox or Sent Items) in the left pane.
• Select Properties.
• Go to the AutoArchive tab.
• Choose either “Archive items in this folder using the default settings” or “Clean out items older than X months” to set custom rules for that folder.
• Click OK.

Method 2: Manual Archive (Export to PST)

1. Export to a .PST file

• Go to File > Open & Export > Import/Export.
• Select Export to a file > Next.
• Choose Outlook Data File (.pst) > Next.
• Select the folder to export (choose the top-most mailbox name to archive everything).
• Check Include subfolders.
• Click Next.
• Choose a destination and filename (e.g., Archive-2024.pst).
• Under Options, select Replace duplicates with items exported (or your preferred option).
• Click Finish. You may optionally set a password for the file.

2. Increase the PST size limit (optional)

• The default PST size limit is 50 GB. It can be increased to 100 GB by editing the registry.
• Open the Registry Editor and navigate to HKEY_CURRENT_USER\Software\Microsoft\Office\xx.0\Outlook\PST (replace xx with 16, 19 or 365 as appropriate).
• Create or modify the MaxFileSize (DWORD) value and set it to 0x1900000000 (107374182400 bytes / 100 GB).
• Create or modify the WarnFileSize (DWORD) value and set it to 0x1400000000 (85899345920 bytes / 80 GB) to receive a warning before reaching the limit.
• For detailed steps, see How to update Windows and apply registry changes.

3. Finalising the archive (backup strategy)

• Close the archive file – in Outlook, locate the archive in the left navigation pane, right-click the archive name and choose Close “<Archive Name>”.
• Copy the .pst file to an external hard drive or approved network location.
• Remove it from Outlook via File > Account Settings > Data Files, select the archive and click Remove.

Method 3: Online Archive (Exchange / Microsoft 365)

• If your organisation has “Online Archive” enabled, Outlook will display an Online Archive mailbox in the left pane.
• Emails are moved automatically based on IT-admin policies – no local PST is required.
• This method stores data in the cloud, saving local disk space.

Australian Small Business Considerations

• ATO record-keeping requirements: The Australian Taxation Office generally requires businesses to keep financial records for at least five years. Ensure your email archiving strategy retains relevant financial correspondence for this period.
• Data sovereignty: PST files stored locally remain under your physical control, whereas Online Archive data is stored in Microsoft cloud data centres. Consider where your data resides and whether it meets your business or industry requirements.
• Privacy obligations: Archived emails may contain personal information subject to the Australian Privacy Act 1988. Apply appropriate access controls and encryption to local PST files and ensure cloud archiving complies with your privacy obligations.

How to View Archived Emails

• If the file is loaded – locate the archive filename in the left navigation pane (below your main folders) and click to browse.
• If the file is closed – go to File > Open & Export > Open Outlook Data File, browse to your .pst and open it. It will appear in the left pane.

Best Practices

• Do not archive to a network drive while Outlook is open – close Outlook, then move the PST to a network or cloud location for safekeeping. See Cannot access shared network drives for guidance.
• Store PST files on a local, non-synced drive – avoid OneDrive, SharePoint or other cloud-synced folders.
• Name files descriptively – include dates or project names (e.g., Warren_Home_Emails_Archive_2025.pst).
• Backup archives – the PST file itself is a backup. Protect it with appropriate NTFS permissions and, if required, a password.

Troubleshooting

• AutoArchive not running – verify that “Run AutoArchive every X days” is enabled, that the interval has elapsed, and that no Group Policy is disabling the feature. You can manually trigger it via File > Info > Cleanup Tools > Archive….
• “File is in use by another program” – ensure the archive is not open in Outlook and that Outlook is fully closed before copying or moving the file.
• Errors during Export – often caused by corrupted items. Use ScanPST on the source PST first, then retry the export.
• PST file will not open – confirm the file path is correct and that you have read/write permissions. Run ScanPST to repair the file if necessary.
• Online Archive mailbox not visible – confirm your Exchange Online licence includes archiving and that your administrator has enabled the feature for your mailbox.
• Registry changes not taking effect – restart Outlook after editing the registry. Ensure you edited the correct Office version key (e.g., 16.0 for Outlook 2016, 19.0 for Outlook 2019, or 365 for Microsoft 365).

Small businesses without dedicated IT support should seek professional assistance before modifying the registry or managing critical email archives. Open a Ticket

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