How to configure the size limit for both (.pst) and (.ost) files in Outlook

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Microsoft Outlook 2016, Outlook 2013, Outlook 2010, Outlook 2007, and Outlook 2003 support 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

Note The WarnLargeFileSize and WarnFileSize registry entries do not enable Outlook to warn you before the file size limit is reached.

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 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.

Outlook 2016, 2013, and 2010

Name Type Valid Data Range Default
MaxLargeFileSize REG_DWORD 0x00000001 – 0x0000C800 0x0000C800 51,200 (50 GB)
WarnLargeFileSize REG_DWORD 0x00000000 – 0x0000BE00 0x0000BE00 48,640 (47.5 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)
Office Version The policy location for the registry entries is located in the following path in Registry Editor The user preference location for the registry entries is located in the following path in Registry Editor
Outlook 2013 HKEY_CURRENT_USER\Software\Policies\Microsoft\Office\15.0\Outlook\PST HKEY_CURRENT_USER\Software\Microsoft\Office\15.0\Outlook\PST
Outlook 2010 HKEY_CURRENT_USER\Software\Policies\Microsoft\Office\14.0\Outlook\PST HKEY_CURRENT_USER\Software\Microsoft\Office\14.0\Outlook\PST
Outlook 2016 HKEY_CURRENT_USER\Software\Policies\Microsoft\Office\16.0\Outlook\PST HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Outlook\PST