If you are using POP3 for email, your email messages get stored in a PST file on the local computer. A .pst file contains all of your Outlook folders, like the Inbox, Calendar, and Contacts and any other folders you have created. There is no automatic backing up of this PST file in Outlook 2003, however Microsoft has released an Outlook 2003 Add-in that can add this functionality.

After downloading and installing the Personal Folders Backup Add-in, select File | Backup to bring up the backup dialog box.

Press Options to specify how often to remind you to backup and where to save the backups to. This can be a local drive or a mapped network drive. You can also specify which PST files to backup if you have more than one.

With the Add-in setup every 7 days you will recieve a small popup reminding you to backup your Personal Folders. Press the button labeled Save Backup and your PST will be backed up automatically the next time you close Outlook!

For more information see:

Download Details: Outlook 2003 Add-in: Personal Folders Backup