Managing PST Files in Microsoft Outlook

Alternatively, to change the default path that Outlook uses when creating a new PST file, you can create a registry entry specific to the user. This value works for Outlook 2007, 2003, and 2002. Open your registry editor, and navigate to HKEY_CURRENT_USER Software\Microsoft\Office\version number Outlook. (The version number for Outlook 2007, 2003, and 2002 and are 12.0, 11.0, and 10.0, respectively.) Add a new string value called ForcePSTPath with the full path as the value. A registry file for this entry for Outlook 2007 would resemble

[HKEY_CURRENT_USER\Software\
Microsoft  Office\12.0\Outlook]
“ForcePSTPath”=”C:\\email”

When creating a new Outlook Data File, Outlook will open this folder location for the user to save his or her new PST file. This location also applies to new OST files.

Configure a Maximum PST and OST File Size
Although Unicode PST files have a theoretical maximum size of 33TB, they still have a default size limitation of 20GB. You can amend this threshold lower or higher through the registry. Certainly, larger PST files aren’t going to perform as well; even 20GB is quite excessive. An administrator or user might want to prevent uncontrolled growth of personal folders on client workstations because of backup and restore resource requirements, prevention of performance degradation, or even disk space concerns. My recommendation would be to limit the size to around 10GB–12GB. To do so, you can configure a user setting at HKEY_CURRENT_ USER\Software\Microsoft\Office\version
number\Outlook\PST or a policy setting at HKEY_CURRENT_USER\Software\
Policies Microsoft\Office\version number\Outlook PST. Again, the version number applies to the version of Outlook (and Office).

You can create four entries for each of these registry locations. The DWORD values that control this setting for Unicode PST files are MaxLargeFileSize and WarnLargeFile- Size. The latter value doesn’t actually warn the user, but it does let Outlook continue with internal operations while preventing the arrival or creation of additional content. (The PST file can still marginally expand as a result of internal processes when the WarnLarge- FileSize value is reached.)

ANSI PST files have a similar control but with smaller values. Because ANSI PST files still have the 2GB limitation, their registry entry is in bytes and the word Large is removed from the DWORD value names. If the MaxFileSize for an ANSI PST file is set beyond the 2GB limit, the value is ignored.

An example of these registry settings for an Outlook 2007 user with the default values would resemble

[HKEY_CURRENT_USER\Software\Microsoft\ 
  Office\12.0\Outlook\PST] 
“MaxLargeFileSize”=dword:00005000
“WarnLargeFileSize”=dword:00004c00
“MaxFileSize”=dword:7bb04400
“WarnFileSize”=dword:74404400

The above DWORD values are in hexadecimal format. You can easily push out these registry entries through Group Policy, the Microsoft Office Resource Kit tools, logon scripts, or another remotemanagement application.

Disable PST/OST Creation
Sometimes in an Exchange environment, you actually want to prevent users from using PST files. Perhaps you have a server-side archive solution, or access to workstations is too insecure for email storage; in such cases, you might require that all content remain in a centralized location. Again, you can accomplish such a configuration through a registry entry that you can then push to systems through Group Policy, logon scripts, the OCT for Outlook 2007, or the CIW for new Outlook 2003 installations. You could also use your registry editor to manually perform the configuration.

Navigate to HKEY_LOCAL_MACHINE SOFTWARE\Microsoft\Office\version number Outlook, and create DisablePST—a DWORD entry with a decimal value of 1 to toggle it on. This value removes the Outlook Data File option from the File, New menu in Outlook, as well as the File, Archive option. It also prevents the creation of OST files and archive PST files and disallows exporting to or importing from other PST files.

Flexibility and Stability
Newer Unicode PST files bring greater flexibility and stability to managing messaging data with Outlook 2007 and Outlook 2003. Different companies will have different needs regarding email storage, and PST management might be part of that administrative challenge. Remember that you have options available to you for controlling PST file location and size—and even for preventing their use.