Allow larger OST and PST file.

Via the Registry

To increase the maximum size of pst-files and ost-files in Outlook, you’ll need to create and set 2 values in 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
  • Outlook 2016 / Outlook 2019 / Microsoft 365
    HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Outlook\PST

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)

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