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Outlook can become unstable if the PST file is too large. There are several ways to save and archive old emails and folders.

I've having problems with my Outlook PST. I think part of my problem could be too many files and folders. I'm a recruiter and I save endless messages in folders in Outlook as a running documentary of each search. I've not been able to figure out a way to transfer this data out of Outlook. The only suggestion to date has been to copy/paste each message into Word. I have 671 folders and 15,353 items in Outlook. So copy/pasting into Word might take months. If you have any other suggestions, I'd appreciate it.

In this excerpt from Answercast #71, I look at ways to manage large Outlook PST files.

Cleaning up Outlook folders

Yes, I actually have a comment and a suggestion.

To begin with, even though those numbers feel kind of large, 671 folders and 15,000 items, that's actually not that huge. I'm convinced that I have way more: certainly in items. Folders? Yeah... I suppose it's a larger than normal - but it's not a number that concerns me. I'll put it that way.

What might concern me would be the overall size. In other words, if those were 15,000 small email messages, that's very different than 15,000 huge email messages. So that's something else to consider when you're looking at the PST as a potential source of problems.

Multiple PST files

Now, my suggestion in general is not to deal with this Word thing. You're right; that's unworkable. Instead, create another PST.

What most people don't realize is that Outlook can easily handle multiple PST files at the same time.

What you do is you use the "File menu." Then there's a "Create New." A data file is what you end up wanting to create. You get to specify the location of the file, which can be any location on your computer of your choosing. Then it creates a brand new Outlook data file, an Outlook PST file. It will show up in the navigation area on the left hand side of your Outlook screen with a set of folders.

Now, all you need to do is drag and drop whatever you want out of your existing PST into your new one. Yeah, that will take a few minutes to copy, depending on the size of the email messages, but it's a very handy way to break things up.

Organize PST files

What I was doing, when I was using Outlook as my email client, is I would create a new archive PST once a year at the end of every year. So I would have, like, 2005.PST, 2006.PST and so forth. I would copy over, or actually move over those things I wanted to save from my regular PST, from my day-to-day PST, and archive it in those separate PSTs.

Then it's totally up to you whether you even need to have those PSTs open. You can always do a "file open" on them later, or you can have them open all the time. What's important is that you move things out of your existing PST. In other words, you would take a bunch of folders for, maybe, some of the searches that you don't expect to ever have to look at again.

You simply drag and drop those into the new PST that you've created, delete them from the old one.

Compact the current PST

After you're done with that process, after you're certain that all of the email is where you expect it to be, then make sure to right-click on the original PST in Outlook and select Properties. Somewhere in there is the option to "Compact the PST."

Much like the file system, when you delete mail out of an Outlook PST, the space isn't actually physically recovered. It's just marked as being unused. The compaction process will actually make the physical PST smaller, and in the process it actually should speed up Outlook's access of that PST.

My guess is that I don't know what kind of exact problems you're having with Outlook but if they're PST related, spreading the load over some number of PSTs and keeping your active PST smaller will probably go a long way to making things a little bit more stable for you.

Article C6044 - November 19, 2012 « »

Leo Leo A. Notenboom has been playing with computers since he was required to take a programming class in 1976. An 18 year career as a programmer at Microsoft soon followed. After "retiring" in 2001, Leo started Ask Leo! in 2003 as a place for answers to common computer and technical questions. More about Leo.

Not what you needed?

david b
November 19, 2012 9:50 AM

I am an Outlook junkie with a PST that's over 860 MB, and still manages to open in a couple of seconds. The giant win for me is the integration with Windows Search. I'd be in real trouble without that feature.

Do other mail clients also integrate well with Windows Search?

Some do. My understanding is that Thunderbird can, but it's not something I ever use. (My experience with Windows search has turned me off ... resource hog when indexing, mostly.)

November 20, 2012 9:47 AM

I always feel it's important to mention that when creating a PST file, don't put it on another computer over a network. Outlook will allow it but it's highly frowned upon. Here's MS's take on it...

November 20, 2012 10:09 AM

Creating a new PST needs a bit of thought.

When you create one, Outlook usually wants to create it on your C: drive. At work, people found it to be problematic whenever they changed desks (hence they got a different PC) - their personal PST folder was no longer accessible. The trick was to use the employee's personal space on the network drive to save the personal PST file.

Of course this can have a downside too. I use a laptop, and by saving the PST on the network drive, I lose access to the PST whenever I leave the office.

As others have commented already I strongly recommend against putting a PST on a network share and accessign it over a network. It's easily corrupted in those situations. To resolve the issue you're describing I'd simply place the PST in a different folder elsewhere on the same machine, or move it to a new location on that new machine. There's really no reason the accessibility problem couldn't be solved.

November 20, 2012 11:09 AM

@James, Microsoft says that's bad advice.

Al Lowe
November 20, 2012 12:58 PM

My PST is 2GB and I'm still running good ol' O2003 and it opens in seconds. But I obviously need to shrink it however I can.

One trick is to sort your Sent Mail by size and delete any email over 1MB (or so). Do this only IF you also have the data somewhere else. I often forward large files. A few hundred 5MB emails will really swell your PST.

Jesse Beck
November 20, 2012 4:03 PM

My Outlook .pst file is a little over 8.6GB. I have over 5 years worth of data in there and absolutely need the search feature(s) for my business. I used to back it up onto external hard drives and flash drives when it was way smaller but due to the 4GB limit, I have to transfer manually to another computer for backing up. I prefer backing up the actual .pst file instead of using the export feature as that way, it keeps all my saved autofill email addresses.

Michael Horowitz
November 20, 2012 4:11 PM

Although I use Thunderbird rather than Outlook, I archive emails using Leo's system too. That is, I create folders called inbox2007, inbox2008, inbox2009, etc. Ditto for the Sent folder. Every six months or so I populate these archive folders. It has worked well for years.

November 20, 2012 8:10 PM

Great advice on archiving and labeling those archives!

I was surprised that this article didn't mention the free tool included with Windows that acts like chkdsk for your PST. It is called SCANPST.EXE and can be found in various folders depending on your version of Office. Do a Windows search for the file and run it. You then select the PST file that you want to scan/repair and it runs for a while. After a reboot, you can test things out to see if this fixes the problem.

Outlook 2007 and beyond should have no problem working with PST files in excess of 4GB. With versions of Outlook before 2007, it is best to keep the PST files below 4GB to prevent corruption.

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