On each folder that needs to be cleaned out regularly, configure AutoArchive to delete items older than a specific number of days then configure AutoArchive to run as frequently as every couple of days or just once a week.

For example, you may want to configure AutoAchive to delete messages from the Junk E-mail and Deleted Items folder that are older than 3 days but keep messages in RSS feed folders for 20 days. If you configure AutoArchive to run weekly, you'll have Junk E-mail up to 10 days old and RSS feeds up to 27 days old.

Right-click on the folder to be archived and choose Properties, then the AutoArchive tab. Select "Archive this folder using these settings" and choose the "Clean out items older than time period." When configuring Autoarchive on Deleted Items, Junk E-mail and your RSS folder, you'll want to select "Permanently delete old items." Click Apply.

If you don't have a global autoarchive setting configured, Outlook will warn you and set it for the default of 14 days. Change the default global setting using the dialog at Tools, Options, Other, AutoArchive. In most cases, you'll just want to change the Run AutoArchive every xx days option and keep the remaining settings on default. Unless you explicitly enabled a folder for AutoArchive or pressed the button to apply the setting to all folders, only the folders you configured for AutoArchive will be archived.

Administrators may want to force the cleanup of deleted and junk items on Exchange server accounts and can configure Mailbox Manager to delete old items from all mailboxes on the server. From the Exchange System Manager, open the Recipients container, then Recipients policy. Right click in the blank area under default policy and choose New, Recipients Policy. Add a check to Mailbox Manager Settings and click Ok and enter a name for your new policy.

If the policy applies only to specific users, click the Modify button on the General tab to configure filters. Choose the Mailbox Manager Settings tab to choose the folders you want to apply the policy to. By default, all folders are selected. In most cases, you'll only want to apply the policy to the Deleted items folder and junk or spam folders. Some sites also use it to clean out old appointments and journaled items to conserve mailbox space, processing only items over a specific size or age.