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Outlook Split PST File: How to Do It

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Outlook Split PST File: How to Do It

If you have a large Outlook PST file that is slow to open or nearing the 50 GB size limit, you can split it into smaller files using Outlook’s built-in archive feature or by creating a new PST and moving items manually. This article explains both methods, how to choose between them, and what to watch out for.

Why Split a PST File?

Outlook stores your emails, contacts, calendar items, and other data in a Personal Storage Table (PST) file. By default, Outlook 2013 and later versions have a PST size limit of 50 GB (though some versions allow up to 100 GB with a registry change). When a PST approaches that limit, you may see errors, the file may become corrupted, or Outlook may run slowly. Splitting the PST into smaller files can improve performance and make backups easier.

Method 1: Use Outlook’s Archive Feature

The simplest way to split a PST is to use the built-in Archive function. This moves older items to a separate PST file, leaving your main PST smaller. Here’s how:

  1. In Outlook, go to File > Options > Advanced.
  2. Under AutoArchive, click AutoArchive Settings.
  3. Choose a folder you want to archive (or select “Apply these settings to all folders”).
  4. Set the archive options: choose a date range (e.g., archive items older than 6 months), and select “Archive items in this folder using the default settings” or customize.
  5. Under “Archive items to”, click Browse to choose where to save the archive PST file.
  6. Click OK to start the archive process.

This creates a new PST file with the older items, and those items are removed from the original PST. The original PST is now smaller.

Method 2: Manually Move Items to a New PST

If you want more control over what gets moved, you can create a new PST and drag items into it. This is useful if you want to separate by project, year, or account.

  1. Go to File > New > Outlook Data File.
  2. Choose the type: Outlook Data File (.pst) is standard. Name the file and choose where to save it.
  3. The new PST appears in the folder pane (usually at the bottom).
  4. Drag emails, contacts, or whole folders from the original PST to the new one.
  5. After moving items, you can right-click the original PST and choose Close to remove it from the view (it remains on disk).

This method gives you full control but takes more time if you have many folders.

How to Choose the Right Method

  • Archive is best when you want to automatically move items older than a certain date. It’s a one-time setup.
  • Manual move is best when you want to organize by category, project, or year, and you don’t mind doing the work.
  • If you need to keep the original PST intact (e.g., for legal or compliance reasons), archive is safer because it removes items from the original, but you can still back up the archive.

Common Problems and Solutions

Problem: After archiving, some items seem missing.
Solution: Check the archive PST file. In Outlook, go to File > Open & Export > Open Outlook Data File and select the archive PST. The items are there, just in a different file.

Problem: The archive PST is also getting large.
Solution: You can archive the archive. Repeat the process on the new PST, or move items to another PST.

Problem: Outlook won’t open the PST at all.
Solution: Use the built-in repair tool. Close Outlook, then run Scanpst.exe (located in the Outlook installation folder, usually C:\Program Files\Microsoft Office\root\Office16). This can fix minor corruption.

Costs and Tools

Splitting a PST using built-in features is free. However, if you have a very large or corrupted PST, you might consider third-party tools. These are not free, and you should only use them from reputable vendors. They can split PSTs automatically, but they are not necessary for most users. Always back up your PST before using any third-party tool.

Safety and Best Practices

  • Always back up your PST file before splitting. Copy the .pst file to another drive or cloud storage.
  • Close Outlook before moving or copying PST files to avoid file locking.
  • Keep your main PST under 25 GB for optimal performance, even though the limit is higher.
  • If you use Outlook with an Exchange account, consider using online archives instead of PSTs, as they are managed by the server.

Frequently Asked Questions

Does splitting a PST delete my emails?

No. Splitting moves emails to a different PST file. They are still in Outlook, just in a different location. You can always open the new PST to see them.

Can I split a PST without Outlook?

You can use third-party software, but they are not free. The built-in methods require Outlook. If you don’t have Outlook, you can’t easily split a PST because it’s a proprietary format.

What is the maximum size for a PST file?

In Outlook 2013 and later, the default limit is 50 GB. Some versions allow up to 100 GB with a registry change, but that is not recommended for stability.

Will splitting a PST speed up Outlook?

Yes, usually. A smaller PST file loads faster and uses less memory. If Outlook is slow due to a large PST, splitting it can help.

Can I merge PST files later?

Yes. You can open multiple PST files in Outlook and drag items from one to another to merge them. There is no built-in merge command, but manual dragging works.

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