How to Break Or Divide An Oversized PST File Into Multiple PST Files?

An oversized PST file is vulnerable to damage and corruption due to integrity issues and inconsistencies that develop when it exceeds a certain limit. As per Microsoft, a PST file under 10GB performs efficiently with Outlook and does not impact the Outlook performance on most hardware. However, if the PST file exceeds 10GB, users may start experiencing slow load time, delay in sending/receiving emails or search results. It may also result in corruption, leading to sync errors and other PST file-related errors preventing users from accessing their mail items.

To prevent such a scenario and avoid PST corruption, you should keep the PST file size smaller, preferably under recommended limits.

In this article, we have shared some solutions to split or break a large or oversized PST file into multiple smaller PST files based on parameters, such as date, email ID, etc. This will help you manage your mail items efficiently and prevent data loss due to PST file corruption.

Methods to Break or Divide an Oversized PST into Smaller PST Files

To split, divide or break a large-sized PST file into multiple smaller PSTs, you can use any of the following methods based on your preferences and requirements.

Export Mail Items to New PST

You may use the Outlook import/export wizard to save mail items or folders from your current Outlook profile or PST to a new PST file. After saving or exporting the mail items or folders to the new PST, you may remove them from your current PST file to reduce its size. Further, you may repeat the steps to export all mail folders in a separate PST file.

The steps are as follows:

  • In Outlook, go to File> Open & Export> Import/Export
  • Select Export to a file and click Next.


  • Choose Outlook data file (.pst) and click Next.
  • Choose the folders you want to export to PST and select the Include subfolder option. Click Next.
  • Click Browse to choose a save location and then click Finish
  • You may enter a password or click OK without entering one. This will export and save the selected mail items or folders into a PST file. You can open and access this PST file in your Outlook.
  • Similarly, you can export other mail folders or items and create more PST files.
  • Once you have exported the mail items, you may delete them from the default PST file to reduce its size. 

Manually Move Mail Items to Local PST

To split or divide a large PST file into smaller PST, you may create a local PST file and move mail items or folders from the existing PST file to this new local PST file. The detailed steps are as follows:

  • Close Outlook and open Control Panel
  • Find and click Mail.
  • Click Data Files and then click Add.


  • Select a location where you want to save the new PST file and click Save.
  • The PST file will be visible in the left pane. You right-click on the file to create a new folder.
  • After creating a folder, you may select the mail items from your large PST file opened in Outlook and move them to the newly created PST file using drag/drop. 
  • You may also select the mail items or folder, right-click and choose Move> Other Folder.


  • Then select the folder in the new PST file and click OK. This will move the mail items and reduce the PST size. 
  • You may create such multiple PST files and move other mail items or folders to split the data between multiple PST files. 

Archive Mail Items into Multiple PSTs

Archiving emails is one of the best methods to reduce the PST file size, organize emails, and keep the PST file smaller. Outlook creates a PST file and saves the archived emails in the file for local access when you auto-archive or manually archive emails in Outlook. 

You can use the archive feature to create multiple archives based on date or folders and divide or break large PST files. The steps are as follows:

  • In Outlook, navigate to File> Info> Cleanup Tools> Archive or File > Info > Tools > Clean up old items.
  • Select Archive this folder and all subfolders, and choose the mail folders you want to archive.
  • You may also choose a date from the Archive items older than option. Outlook will archive mail items from the folder received before the selected date.


  • This way, you can create multiple .pst files based on the email folder and split or device the PST.

NOTE: Archived emails are automatically purged from the Outlook PST file. 

Use PST Splitter Software 

A PST splitter software, such as Stellar Splitter for Outlook, can also help you efficiently divide, break or split an oversized or large PST into smaller PST files with complete integrity and precision. Unlike manual options where you need to repeat several steps to divide large PST files, the software does this automatically. In addition, you can divide or split a PST file based on various parameters, such as a specific date range, file size (between 5-50GB each), email address, or folder.


All you need to do is choose the desired criteria for splitting the PST file, choose a save location and leave the rest to the software. It automatically breaks the PST file and its contents into equivalent sizes at your desired location, such as emails, attachments, contacts, notes, tasks, etc. 

Most importantly, it preserves the original structure and hierarchy of mail items intact after splitting the PST file. You can download the demo version to get started and evaluate the software before purchasing the license key. 

To Wrap Up

Splitting PST files helps manage large PST files and avoid damage or corruption, leading to data loss. Besides, large PST files are known to cause Outlook performance issues, such as delays in sending or receiving emails, synchronization issues, slow load times and search results, etc. In this article, we share some reliable methods to split, divide, or break a large or oversized PST file into smaller PST files and reduce the PST file size to avoid consequences leading to a data loss situation. Keeping the PST file small can significantly improve the Outlook performance and may resolve common Outlook issues, as discussed in the article. 

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Osho Garg

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Osho is Tech blogger. He contributes to the Blogging, Gadgets, Social Media and Tech News section on TecheHow.