How to Merge Two PST Files in Outlook Into One Archive

You may have multiple Outlook Data Files (PSTs) from old accounts or archives that you want to combine. Managing separate files for similar data is inefficient and makes searching difficult. This article explains how to merge two PST files into a single, organized archive using Outlook’s built-in import and export tools.

Understanding PST Files and the Merge Process

A PST file is a local data file used by Outlook to store emails, calendar items, contacts, and tasks. You might have one for an old email account and another for archived items. Merging them involves copying the contents of one or more source PST files into a single destination PST file. The process does not delete the original source files, keeping your data safe. You need to have both PST files added to your Outlook profile and visible in the folder navigation pane to perform the merge.

Steps to Merge PST Files Using Import/Export

The most reliable method uses the Import/Export wizard. This ensures all item types and their properties are transferred correctly.

1. Open the Import/Export Wizard
   In Outlook, go to File > Open & Export > Import/Export. This starts the wizard.
2. Select the export action
   Choose “Export to a file” from the list and click Next. Then select “Outlook Data File (.pst)” and click Next again.
3. Choose the source folder
   Select the top-level folder of the PST file you want to merge from. To include all subfolders, check the box for “Include subfolders”. Click Next.
4. Browse to the destination PST
   Click Browse and navigate to the PST file you want to merge into. This is your target archive file. If you need a new file, you can create it here by typing a new name.
5. Set duplicate handling
   Choose how to handle duplicate items. The option “Do not export duplicate items” is usually best for a clean merge. Click Finish.
6. Optional: Add a password
   You can set a password for the destination PST file in the dialog that appears. This step is optional. Click OK to start the export and merge.

Steps to Merge PST Files Using Drag-and-Drop

For smaller merges or selective copying, you can use drag-and-drop within the Outlook interface.

1. Add both PST files to Outlook
   Ensure both the source and destination PST files are added to your profile. Go to File > Account Settings > Account Settings. Switch to the Data Files tab and click Add to open a PST if it is not already listed.
2. Arrange the navigation pane
   In the folder navigation pane, expand the folders for both PST files so you can see the source and destination folders.
3. Select and drag items
   Select the folders or items you want to merge from the source PST. Drag them and drop them onto the target folder in the destination PST file. Hold the Ctrl key while dragging to copy items instead of moving them.

Common Mistakes and Limitations

Outlook Says the PST File is Not Accessible

This error often means the PST file is already open in another program or is located on a network drive with permissions issues. Close any other mail applications. Move the PST file to your local drive, like the Documents folder, and try adding it to Outlook again.

Duplicate Items Appear After Merging

If you run the import/export process multiple times without selecting “Do not export duplicate items,” you will create copies. Use the Clean Up Tools in Outlook to find and remove duplicates after the merge. Go to the Folder tab and select Clean Up Folder.

The Merged PST File Becomes Too Large

Older PST files have a size limit of 20 GB for Outlook 2010 and later, and 2 GB for older formats. A merge can push a file near this limit. To avoid corruption, consider creating multiple archive PST files by date or project instead of one massive file. You can also use the Archive feature (File > Info > Cleanup Tools > Archive) to automatically move older items to a new file.

Manual Merge vs. Import/Export Wizard

Item	Drag-and-Drop Manual Merge	Import/Export Wizard
Best for	Selective copying of a few folders	Merging entire PST files with all data
Handles duplicates	No automatic detection	Yes, with a dedicated option
Risk of error	Higher if dragging many items	Lower, process is automated
Item types transferred	All, but folder permissions may not copy	All item types and most properties
Speed	Fast for small batches	Slower but more reliable for large jobs

You can now consolidate multiple archives into one organized PST file. For ongoing management, set up AutoArchive to automatically move old items to your merged file. Use the Search Folders feature to quickly find content across your large archive without manual browsing.