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Increase maximum size pst-files

I heard that the default size for pst-files is 20 GB but also that there must be a registry value that allows to increase the maximum up to approximately 4PB (4096TB).

How do I increase the maximum file size of an UNICODE pst file?

In Outlook 2003 and Outlook 2007, the maximum size of a Unicode pst-file has indeed been limited to 20GB. In Outlook 2010 and 2013, this limit has been set to 50GB.

You can increase (but also decrease) this limit via the Registry or via Group Policies.

Note: This tip does not apply to pst-files who are in the Outlook 97-2002 format (ANSI formatted pst-files).

Via the Registry

 You need to go to the following location in the Registry;

  • Outlook 2003
    HKEY_CURRENT_USER\Software\Microsoft\Office\11.0\Outlook\PST
  • Outlook 2007
    HKEY_CURRENT_USER\Software\Microsoft\Office\12.0\Outlook\PST
  • Outlook 2010
    HKEY_CURRENT_USER\Software\Microsoft\Office\14.0\Outlook\PST
  • Outlook 2013
    HKEY_CURRENT_USER\Software\Microsoft\Office\15.0\Outlook\PST

Here you must create and set 2 new DWORD values (note that these values are case sensitive);

  • WarnLargeFileSize
    Don’t set this higher than 4090445042 (decimal) or f3cf3cf2 (hexadecimal)
  • MaxLargeFileSize
    Don’t set this higher than 4294967295 (decimal) or ffffffff (hexadecimal)

The first value is how many MB a user can write to a pst-file. The second value is how many MB the system can write to a pst-file. This difference has to be at least 5% since there is more written to a pst-file than just user data.

Registry Editor - Increase the maximum size of your pst-file via the MaxLargeSize key.
Above the maximum size of a pst-file has been set to 100GB with a warning at 95GB.

Via Group Policies

Not comfortable editing the Registry? You can then use Group Policies as well even when you are on a home computer. For instructions on how to use Group Policies see this guide.
The settings for adjusting the pst filesize can be found in the section Miscellaneous-> PST Settings. The following 2 settings need to be modified;

  • Large PST: Absolute maximum size
    Don’t set this higher than 4294967295
  • Large PST: Size to disable adding new content
    Don’t set this higher than 4090445042


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