University of Oregon

Outlook Mailbox Size Reduction



This page explains how to reduce the amount of space needed to store email messages by moving old information to an archive. It applies to anyone using Microsoft Outlook.

Create an email archives folder on your computer

This is the location where your archive files will live. We  recommend creating this on your Desktop so that it is easy to locate.
  1. Minimize all applications so that you're looking at your desktop.
  2. Right-click on your desktop and go to New > Folder
  3. Name your folder "Email Archives" (no quotes).

Organizing your archives

We recommend archiving mail based on date. For example, you could archive by year, and would have a 2007.pst, a 2008.pst, 2009.pst, and so on. You may find it more useful to archive by topic, or other criteria that may be easier for you. If you have a lot of mail, you should try to split it up into a few PST files to reduce their individual sizes. Having a single, very large PST file may cause performance issues, and could be unreliable in the future. If you need assistance deciding what criteria to archive by, please let us know and we'll set up an appointment to go through your mail hierarchy with you.

Archiving Mail

  1. Once you've decided on how you'd like to organize your archives, you can begin the Archive process. For demonstration purposes, we'll archive by year.
  2. Outlook 2010: Click on File, then click on the Cleanup Tools button, and choose Archive.
  3. Outlook 2007: Click on File, then click on Archive...
  4. Select the folder you'd like to archive. If you'd like to archive messages from your entire mailbox, select the very top line, which will usually be labeled after your email address.
  5. Where it says "Archive items older than:" choose a date. Messages received, sent, or modified prior to this date will be archived.
  6. Click the Browse button.
  7. Select the Desktop on the left hand side of the window
  8. Select the Email Archives folder
  9. Change the File name: from "archive.pst" to something relevant, usually the date you entered above. For example, if you are archiving messages older than Jan 2011, you should name this "2010 and older.pst" because it will contain messages from 2010 and older.
  10. Click OK twice until you're back to the File window. Archiving may take some time when you first perform it, but you should be able to continue working in Outlook as it runs in the background. (Outlook can only perform one archive operation at a time.)

Some mail didn't get moved

The archiving function of Outlook looks at the most recent of three dates for each message: the Sent, Received and Modified dates. If a message wasn't moved automatically during Archiving, it is probably because one of these dates (most likely the Modified date) occurs more recently than the date you've set to Archive prior to. Unfortunately, the best solution in these cases is to manually move the message to the Archives folders. To do so:
  1. Select the message
  2. Right-click on the message
  3. Choose Move
  4. Choose Other Folder
  5. Scroll down to Archives
  6. Click the arrow to the left of Archives to expand it
  7. Locate the folder that this message should be placed in, select it, and click OK.

Set up Backups

Now that you have your Archive files on your computer, you should ensure that your data is being backed up to an external hard drive.

Finding Archived Mail

  1. In Outlook, when looking at your Inbox, you should see your folder list on the left hand side.
  2. Scroll down to the bottom of the Folder list and locate the "Archives" item.
  3. Click the arrow to the left of the "Archives" item to expand it.
  4. You should see your Folder hierarchy reproduced here.
    • Note: If you just performed an archive, it may still be in the process of recreating this folder hierarchy.
  5. You can search for your messages here, as you would in normal folders.