Many companies institute storage limitations on their Exchange Server mailboxes. A storage limit of 50MB is common, and even lower storage limits aren't unreasonable or unheard of. A low storage limit means that employees must take various actions on a regular basis to reduce the size of their mailbox. For example, I typically send and receive anywhere from 20 to 50 email messages a day. If each email message is a mere 10KB, I'm adding almost half a megabyte of information to my mailbox every day. If any of the messages I send or receive have attachments, I can easily add more than a megabyte of data to my mailbox each day.
To keep your Exchange mailbox within its storage limits, you could simply purge items from your mailbox every day. Deleting read messages, purging your Sent Items folder regularly, and deleting old appointments, tasks, and journal entries is a surefire way to keep your mailbox size small. Unfortunately, this method also prevents you from referring back to a crucial message you sent 3 months ago or determining exactly when you met with an important client. To keep your mailbox small and maintain a record of important messages and other Outlook items, consider using Outlook's built-in AutoArchiving feature.
By default, AutoArchiving moves messages that are older than a certain date to folders in the archive.pst file, which is typically stored on your local hard disk. Outlook then removes the messages from your Exchange mailbox, saving space and reducing clutter.
To access Outlook's AutoArchiving options, choose Options from the Tools menu, go to the Other tab, and click AutoArchive. The AutoArchive dialog box contains AutoArchive options for your entire mailbox. By default, AutoArchive runs every 14 days; however, you can choose a different interval to meet your particular needs. Outlook archives Calendar, Tasks, and Journal items after 6 months; Deleted Items after 2 months; and Inbox, Drafts, and Notes items after 3 months. The Contacts folder is never archived.
If you have a very low mailbox size limit, you might want slightly more aggressive AutoArchive settings on certain folders. To configure the settings on a per-folder basis, right-click the folder name, choose Properties, and go to the AutoArchive tab.
By default, all items in a folder are archived if they meet the AutoArchive age criteria. However, you can exclude items in a folder from automatic archiving on a per-item basis. For example, if you want to clean out all Inbox items that are more than 3 months old but keep three items that contain information you need on a regular basis, you can do so. To prevent Outlook from AutoArchiving an item, open the item and choose Properties from the File menu. Select "Do not AutoArchive this item" and click OK. Close the item and save your changes.
In Outlook 2003 and Outlook 2002, the archive.pst file should be visible at the top of Outlook's Folder List. The file, called Archive Folders, contains a duplicate of the folders in your Exchange mailbox, and these folders contain any items that Outlook has archived. You can access these items just as you would items in Outlook's regular folders. If you don't see Archive Folders in your Folder List, choose File, Open, Outlook Data File (or Personal Folders File in Outlook 2000 and earlier) and search for the archive.pst file. Opening this file through Outlook will add Archive Folders to your Folder List. (Windows XP and Windows 2000 treat .pst files as hidden files, so before you can find archive.pst, you must enable hidden-file viewing. To do so, open the Folder Options dialog box in Control Panel. On the View tab, select "Show hidden files and folders.")