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Increase maximum size pst-files

I heard that the default size for pst-files is 50 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?

PST and OST File Size buttonIn Outlook 2003 and Outlook 2007, the maximum size of a Unicode pst-file has been limited to 20GB. In Outlook 2010, 2013 and 2016, 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

Regedit.exe buttonTo increase the maximum size of a pst-file in Outlook, you’ll need to create and set 2 values in the following location in the Registry;

  • Outlook 2003
  • Outlook 2007
  • Outlook 2010
  • Outlook 2013
  • Outlook 2016

The following 2 new DWORD values must be created or set;

  • 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 before receiving a warning that the file is full. 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

Group Policy Editor buttonNot 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 file size 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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