Recently my Outlook 2010 OST grew to over 4GB of space which made Outlook slow.


One of the biggest reasons why it’s this large is SSW’s policy against auto-archiving and never permanently deleting anything. As a result my Deleted Items folder was actually 2.1 GB!


Now, I don’t actually need all of those items as they do span back about 4 years. So the goal is to only bring down the current year’s deleted items.

Step 1 – Organise the deleted folders into years

This can be done using the Rules Wizard


Note: Obviously run this rule for each year in the Deleted Items folder

Step 2 – Stop Synchronization with the previous year’s deleted data

  1. Right click on the folder you want to stop Synchronization for (in my example the 2010 folder) and select Properties
  2. Select the Synchronization tab
  3. Click Filter
  4. Click on the More Choices tab
  5. From the Size (kilobtytes) dropdown select less than and set the value to 0
  6. Repeat for any other folders

Note: there is an option to specify an Advanced filter with a Received date range but I haven’t found documentation as to what the syntax of the value should be.


Step 3 – Clear the offline files and Compact the OST

The last step is to clear the offline files then compact the ost file to reclaim the space. You can do this by:

  1. In the folder properties select the General tab
  2. Click Clear Offline Items – this will remove the files locally
  3. You can click on the Synchronization tab and you should see all the items on the server and none locally
  4. Close Outlook
  5. Go to Control Panel | Mail
  6. Select Data Files
  7. Select your OST and click Settings
  8. Select the Advanced tab
  9. Click Outlook Data File Settings
  10. Click Compact Now

Once the process finishes you will notice your OST shrink considerably if you have lots of deleted items. For me my OST is now 2.1GB instead of 4GB



Things to note:

  1. The deleted items are still stored on exchange, they are just not being downloaded locally
  2. You can still see the files in any other client, including Outlook Web Access
  3. Beats using Auto Archive Smile