Cleaning your Outlook.pst File

It’s a little known fact that Microsoft Outlook has a 2GB limit on the size of its .PST file (Increased to 20GB in Outlook 2003) and whilst this isn’t usually a problem for most people, it can quickly become full if you start sending / receiving E-mails with large video files, pictures etc. Which in these days of high speed broadband access is pretty common.

Having too large a profile can also drastically affect the way Outlook performs, and if yours is made up lots of E-mail messages, imagine how difficult it must be to find that important one you were looking for!

Obviously the first thing to do is find out how big your current profile is, do this:

  • Make sure the folder list is visible.
  • Right Click the ‘Outlook Today’ folder at the top of the folder list and select ‘Properties’
  • You will then be presented with the Properties window where you can view some general information, to get the information we want click on the ‘Folder Size’ button.
  • You will now be presented with a window where you’ll see an overview of your profile, along with the size of the individual folders. Have a look at these folders, and decide which ones you need to reduce the size of.


We have listed them here in the order that you are most likely going to need to clean.



This is probably one of the biggest folders in your profile, considering every E-mail you ever receive goes into this or one of its sub folders it’s hardly surprising. Start by sorting through your messages and deleting all those that you no longer need, maybe they are just greetings from friends or relatives, or newsletters that you’ve subscribed to. Next look for all those large E-mails that maybe have attachments, do you need the attachment still? If so save it to your hard drive or CD and delete the original.

Sent Items

Every E-mail item you send out is stored in the ‘Sent Items’ folder by default, which can get pretty clogged up if you send lots of attachments. Cleaning this folder up is generally similar to cleaning up your Inbox, although you can probably safely delete all messages with attachments as you must have them stored somewhere else on your system in order to attach them to an E-mail!. If you want to keep the messages but not the attachments then Open the message, right click the attachment and select the ‘Remove’ option, then Save and close the message.

Junk Mail

It’s a sad fact of life now that everyone needs to have a ‘Junk Mail’ mailbox to put all the spam you receive in. This is quite easy to clean, have quick look through just to make sure that the mail filter hasn’t accidentally classed a good item as junk (If it has just copy it to the appropriate folder). Next select an item in the folder then hit Ctrl+A to select all items, and then hit the delete button.


Has anyone ever found a real use for the Journal? We suspect not, unfortunately it’s pretty easy for the Journal folder to fill up of its own accord by creating a log of things you work on during the day. If you don’t use the Journal, have a look inside to see if there are any entries, if there are then the option to activate the Journal is probably switched on, to disable it select Tools from menu bar, then Options then ‘Preferences’ Tab and click the button ‘Journal Options’ You will then see a dialog where you can select which items you want added to the Journal. Un-selecting all items will disable the journal. Deleting items from the Journal can be an arduous task at best if it’s in its default view of ‘Timeline’ so switch to ‘Category’ view then delete all items by selecting them and deleting.


The Calendar is generally not a problem for most people as items are usually just plain text and only take up 1-2kb in general. If your Calendar folder looks quite big then you may have documents, or pictures attached to an item(s), hunt the offenders down and delete what you don’t need.


The Task list is probably one of the easiest to clean, look for all the things you’ve done and delete them. It’s a pity there’s no ‘auto remove’ function to remove those items that have been marked as complete after a set number of days. If anyone from Microsoft is reading this then please look into adding it!


As with the Calendar, each entry in your contacts takes up very little space, so unless you have lots of very old contacts that you’re never going to need again then you won’t save much by weeding this out. The only exception to this is in Outlook 2003 where you can store pictures with each contact, these should be used sparingly to avoid increasing the size too much.

Deleted Items

As with Windows itself, deleting items in Outlook doesn’t get rid of them until you’ve deleted the ‘Deleted Items’ Folder, so remember to do this on a regular basis. We would suggest that you consider turning on the option to delete all deleted items every time Outlook exits (Select Tools –> Options –> Other –> Tick the box marked ‘Empty the deleted items folder on exiting’.)

Compacting Your .PST File.

If you are concerned enough to check your .PST file size before and after you cleanse your folders then you will notice that its size hasn’t changed which is something that catches people out. You will now need to compact your .PST file to remove the empty space.

  • Go to Folder view and right click on ‘Outlook Today’
  • Select ‘Properties For Outlook Today’
  • From the dialog click the ‘Advanced’ Button
  • Now click the button marked ‘Compact Now’


Depending on the size of your .PST file this may be quite quick, or fairly lengthy. It has also been reported that the compaction process needs to be done two or even three time in quick succession to achieve the best results.