Splitting a pst-file into yearly archives

Splitting a pst-file can be done via the Archive feature in Outlook. To split it into yearly archives (or any other amount such as quarterly, or every 2 years), you can run the Archive process multiple times, each time to a new pst-file.

Note: The definition of a “large pst-file” is somewhat relative and on most systems having a pst-file of 4GB or even 10GB is no problem at all. Of course, the backup process will take a bit longer. For more info, also see: How often do I need to use AutoArchive?

Step 1: Set Outlook to archive by Received Date

Before you start, you must configure Outlook to archive based on the Received date rather than the Modified date. This way, you prevent emails which have been modified or imported after your archive date from remaining in your main pst-file.

The process to do this is described in the previous tip:
Archive based on Received instead of Modified date

Step 2: The Archiving process

Now that Outlook is prepared, you can split your pst-file in the following way:

1. Open the Archive dialog.
   • Outlook 2007
     File-> Archive…
   • Outlook 2010 / 2013 / 2016 / 2019 and Microsoft 365
     File-> Cleanup Tools-> Archive…
2. Select: Archive this folder and all subfolders
3. Click on the top level folder to select the entire mailbox rather than the currently selected folder.
4. Set the “Archive items older than:” date to the 1st of January of the year after you want to create your first archive for. So if you want to create your first archive for 2011 and previous, set the date to the 1st of January 2012.
5. Optionally, check the option: Include items with “Do not AutoArchive” checked.
6. Specify a name and a location for your pst-file for 2011 and previous. Make sure that this is a location on your local computer and not a network share.
   Example: D:\Documents\Outlook Files\2011.pst
7. Click OK.

After archiving has finished, repeat the above steps but specify a different date in step 4 and a different name in step 6.

You can use the Archive feature to split your pst-file.

Step 3: Compact Now and updating your backup schedule

Once you’re done creating yearly archives, you might notice that your original pst-file still hasn’t decreased (much) in size. This is because a pst-file is a database and, for performance reasons, space freed up by removed items isn’t directly being returned to the file system. This space is called “white space”.

Outlook will automatically return this “white space” when a certain amount of it exists in a pst-file (which can be up to 15 percent) and the computer is idle. To start this process manually and directly return this “white space” as free space on your disk, you can use the Compact Now button. Your pst-file will now decrease in size.

Also make sure that you include these newly created pst-files in your backups. Of course, because you no longer add or remove data to these pst-files, you no longer have to include them in your daily backups and can therefore save yourself some time and space.

PST-Splitter Tools

If you need to split multiple pst-file, then the Outlook based method might not be too efficient, especially when you have a very large pst-file.

In that case, you could consider using one of the following 3rd party tools to split your pst-file(s). These tools also offer other criteria to split the pst-file than by date. For instance; by Size, From or Folders.

• Stellar Splitter for Outlook
• Kernel for PST Split