Archiving Old Emails in Outlook

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 disc 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 0x19000000 (100 GB in decimal).
• Create or modify the WarnFileSize (DWORD) value and set it to 0x14000000 (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 disc space.

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. For further assistance with corrupted items, see Deleted email recovery.
• Online Archive not visible – confirm you have an Exchange Online licence that includes archiving and that the administrator has enabled the feature for your mailbox.

When to Seek Further Assistance

If you reach your mailbox quota, encounter persistent PST corruption, or need to migrate data to a compliant server‑side archive, open a ticket for IT support.

Still Having Issues?