The Joy of Outlook PST Files

Outlook PST files are the nastiest things around. In the past two days I had two users with 1.9GB PST files. According to Microsoft, Outlook XP and below use ANSI encoding which limits the size of the PST file to 2GB. Outlook 2003 and greater uses Unicode encoding which allows PST files to be up to 20 GB. What happens if you go over the 2GB limit in Outlook XP and below? All the data written after the 2GB mark is gone. You have to use a utility called PST2GB to truncate the file. How swell! The funny part about it is that PST files seem to corrupt a lot around here and not even at the 2GB mark. When a PST file corrupts and you are using POP3 as your mail setup, watch out. All the files it downloads during the corruption go into never-never land (because POP3 downloads the messages locally and deletes them from the server. Of course, the files have no where to go). I’ve never seen such a bone headed e-mail program do that. If the PST file is corrupt (trust me, Outlook KNOWS it is corrupt, it will even tell you: “errors detected in PST”), then STOP DOWNLOADING THE USER’S E-MAIL!

The user will call you with messages stuck in the Outbox folder and of course, Outlook not working. You cannot delete the messages in the Outlook folder as Outlook will tell you that MAPI32 has begun transmitting the messages. It seems that Outlook sets a flag in the message that it is being transmitted and that flag cannot be reset easily. The only way to reset the flag is to export the whole 1.9GB PST to a new file (yes, all 1.9GB of it!). First, however, you have to run SCANPST on this monolithic file as it is corrupt. That takes a good 45 minutes. Then you have to export it. Another 20 minutes goes by. Now you can delete those nasty messages from the Outbox folder! The fun has just begun, because you have to start deleting a bunch of messages to get the file size back down.

But wait….you keep deleting files and the size of the PST doesn’t go down. Why? Because you have compact the file! You see, when you delete a message in Outlook, it just creates a blank space or record where the message was. Therefore, the size of the PST file says the same until you run a manual compaction which takes those spaces out of the file. Brillant! The compaction alone took 3 1/2 hours!

Factor in the time of copying the PST file from the user’s workstation to mine, running scanpst, running an export, deleting files from the PST file, running a compaction and copying the file back to the user’s workstation, you will easily spend 6 hours or more fixing the problem!


Thank you 🙂

– Soli Deo Gloria

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