Your .pst File Questions Answered

Sue Mosher answers some of your questions about .pst files.

Sue Mosher

July 28, 2005

5 Min Read
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Oh, how your mistakes come back to haunt you! A colleague recently pointed out a big blooper in "Dealing with .pst Files," my November 2003 article about Personal Folders (.pst) files (see the URL below). In that article, I said that the default maximum size for the new Unicode .pst files that Outlook 2003 supports is 20MB. The default maximum size is, of course, 20GB--not 20MB.

I thanked my colleague, however, because the comment drew my attention to the latest round of reader comments and questions that have been posted to the article. In this week's commentary, I answer some of those questions, providing a little .pst FAQ update. Thanks for the great feedback!

How can I open an Outlook 2003 .pst file in Outlook 2002?

You can't. Only Outlook 2003 can open the new Unicode .pst files. After you open the file in Outlook 2003, you can export it (or at least 1.8GB of its data) to a file that's compatible with earlier versions of Outlook. Create that file with the File, New, Outlook Data File command and choose Outlook 97-2002 Personal Folders File (.pst) as the storage type. You can use the new .pst file as the target in Outlook's File, Import and Export Wizard.

How can I tell what version of .pst file I'm using?

If the version isn't visible in the folder list, open the file in Outlook using the File, Open, Outlook Data File command. Then choose File, Data File Management to see a list of all active .pst files, including any that are used for IMAP accounts or Windows SharePoint Services lists. Select any .pst file, then choose Settings. The Format dialog box will list either Personal Folders File--which means the file is in Unicode format--or Personal Folders File (97-2002)--which means it's in the legacy ANSI format. SharePoint files, by the way, will be in the new Unicode format, whereas IMAP accounts will use a .pst file in the old format.

Is it possible to add two .pst files to an Outlook profile using .prf files?

Yes, it is. The Office Resource Kit tools--the Custom Installation Wizard (CIW) and the Custom Maintenance Wizard (CMW)--that are used to generate .prf files let you add more than one .pst file. You can also use the tools to create a .prf file that modifies an existing profile by adding a new .pst file. One problem is that both the CIW and CMW have a bug that results in their ignoring any attempt to specify the Unicode format for the new .pst file. The solution is to export the .prf file from the CIW or CMW and edit it in Notepad to change one setting under the service section, EncryptionType=0x40000000, to EncryptionType=0x50000000, which adds the particular .pst file. You can then either import the .prf file back into the CMW or CIW or deploy it using the other methods described in the Office Resource Kit.

How can you set up a different data file for each mail account?

IMAP4 and Exchange accounts get their own information stores automatically; IMAP accounts get .pst files in the old format. For POP3 accounts, you can use Outlook's Rules Wizard rules to move incoming messages into different .pst files.

Do .pst files include attachments or does Outlook store them somewhere else?

Yes, Outlook stores all attachments to Outlook items--not just messages, but also Contacts, Tasks, and other items--as part of the item in that .pst file. This process has its pluses and minuses. It certainly simplifies backups because there's only one file to back up or move to another machine. However, it makes the .pst file potentially very large, especially if the user exchanges a lot of large PowerPoint presentations or other large files via email. Many programs are available, both for end users and for administrators, that extract attachments and store them separately to minimize the size of .pst files and mailboxes. Diane Poremsky maintains an excellent list of these programs on the Slipstick Systems Web site.

Is it possible to share a .pst file between users or a folder within a .pst?

Outlook can't share its files directly. However, third-party tools can add sharing capability for users who don't have Exchange mailboxes. See the Slipstick Systems Web site for more information.

My profile shows two .pst files with the same name and the same data, giving me two copies of everything. How can I get rid of one?

It sounds like you might have a "ghost" .pst file--one that appears in the Outlook folder list but doesn't really exist as a separate file. You won't be able to close it with the usual method, which would be to right-click the .pst file's root folder and choose Close. The one sure way to get rid of it is to start over with a completely new mail profile. When you create the new profile, Outlook will create a new default .pst file for that profile. Start Outlook with the new profile, then open the old .pst file you want to use by choosing the File, Open, Outlook Data File command. Then choose Tools, E-mail Accounts, View or change existing e-mail accounts. Under Deliver new e-mail to the following location, choose the file you want to use as your default. After you restart Outlook, you'll be able to close the new .pst file that Outlook created for that profile so that only your original .pst file appears in the folder list. Tip: Always give each .pst a unique display name when you create it or edit its settings in the File, Data Management dialog box. Doing so will make it much easier to distinguish among .pst files in the Tools, E-mail Accounts dialog box.

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