How to configure the size limit for both (.pst) and (.ost) files in Outlook 2003 (832925)

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

MORE INFORMATION

Follow these steps to configure the size limit for both the .pst and the .ost files.

Note The settings that are discussed in this article apply to both .ost and .pst files. If you modify these registries, this can affect .ost files that are used with Cached Exchange Mode, with AutoArchive, and with .pst. files.

Warning If you use Registry Editor incorrectly, you may cause serious problems that may require that you reinstall your operating system. Microsoft cannot guarantee that you can solve problems that result from using Registry Editor incorrectly. Use Registry Editor at your own risk.

Click Start, and then click Run.
In the Open box, type regedit, and then click OK.
In the left pane, expand My Computer, and then expand HKEY_CURRENT_USER.
Expand Software, and then expand Policies.
Expand Microsoft, and then expand Office.
Expand 11.0, and then expand Outlook.
Click PST, and then right-click MaxFileSize in the right pane.
Click Modify, and then type the value in the Value data box.
Click OK.
Right-click WarnFileSize, and repeat steps 8 through 9.
Right-click MaxLargeFileSize, and repeat steps 8 through 9.
Right-click WarnLargeFileSize, and repeat steps 8 through 9.

It is recommended that the values between the MaxFileSize registry entry and the WarnFileSize registry entry, and the values between the MaxLargeFileSize registry entry and the WarnLargeFileSize registry entry be at least 5 percent (%) so that internal processes are not hindered from continuing.

If the value of the MaxFileSize registry entry ever exceeds the ANSI 2 gigabyte (GB) limit on either the .pst or the .ost files, the value will be ignored to limit the size to 2 GB to prevent corruption. The default value for the WarnFileSizeregistry registry entry is calculated to be 95% of the MaxFileSize registry entry for a UNICODE file, and it remains at 1,950,368,768 bytes for small ANSI files.

Note You can set the UNICODE limits beyond the values that are listed in the table. However, we do not recommend doing this because performance can decrease.

If .ost files or .pst files reach the limit that is specified in the WarnFileSize or the WarnLargeFileSize registries, the compaction function is triggered to try to reduce the size of the file to a usable level. When the WarnFileSize or the WarnLargeFileSize limit is reached, e-mail messages cannot be sent (provided that sent e-mail messages are stored in the Sent Items folder), and items cannot be copied or moved within the file. If the file is an archive .pst file that is used for AutoArchive, the AutoArchive operation will fail. However, e-mail messages can be deleted or archived from a .pst or from an .ost file that is currently being used as the default delivery location.

The following are some of the errors that may occur when files reach the maximums specified in the registries:

When you try to move items to a .pst or an .ost file that has reach the limit, you receive the following error message:
Can't move the items. The file <path>\<filename>.pst has reached its maximum size. To reduce the amount of data in this file, select some items that you no longer need, and then permanently delete them.
When e-mail messages are delivered to a .pst or an .ost file that are using Cached Exchange Mode, and the file has reached the limit, the Mailbox Cleanup wizard launches.