Harry Bates has written PSTSetMax to configure the size limit for both (.pst) and (.ost) files in Outlook 2003.

When you type PSTSetMax /?, you'll receive a dialog box that looks something like the one shown below:

              

Microsoft Knowledge Base Article 832925 contains the following summary:

Microsoft Office Outlook 2003 supports both American National Standards Institute (ANSI) and UNICODE personal folders (.pst) and offline folder (.ost) files. This article describes how to use the following four registry entries to limit the size of both the .pst and the .ost files:

  • The MaxFileSize registry entry
  • The WarnFileSize registry entry
  • The MaxLargeFileSize registry entry
  • The WarnLargeFileSize registry entry

The MaxFileSize registry entry

The MaxFileSize registry entry determines the absolute maximum size that both the .pst and the .ost files can grow to. After this maximum size is reached, Outlook 2003 does not permit the size of the file to grow beyond this size.

The WarnFileSize registry entry

The WarnFileSize registry entry determines the maximum data that both the .pst and the .ost files can have. After this maximum data is reached, neither the .pst nor the .ost files are permitted to add any more data. However, the size of the physical file may still increase because of internal processes.

In the following table, the MaxLargeFileSize registry entry and the WarnLargeFileSize registry entry refer to a UNICODE formatted (new Large format) file, and the MaxFileSize registry entry and the WarnFileSize registry entry refer to an ANSI formatted (an earlier Microsoft Outlook format) file. The UNICODE values are set in megabyte (MB) increments, while the ANSI values are set in byte increments.

Name Type Valid Data Range Default
MaxLargeFileSize REG_DWORD 0x00000001 – 0x00005000 0x00005000 20,480 (20 GB)
WarnLargeFileSize REG_DWORD 0x00000000 – 0x00005000 0x00004C00 19,456 (19 GB)
MaxFileSize REG_DWORD 0x001F4400 – 0x7C004400 0x7BB04400 2,075,149,312 (1.933 GB)
WarnFileSize REG_DWORD 0x00042400 – 0x7C004400 0x74404400 1,950,368,768 (1.816 GB)

The policy location for the registry entries is located in the following path in Registry Editor:

HKEY_CURRENT_USER\Software\Policies\Microsoft\Office\11.0\Outlook\PST

The user preference location for the registry entries is located in the following path in Registry Editor:

HKEY_CURRENT_USER\Software\Microsoft\Office\11.0\Outlook\PST