Use AutoArchive to delete messages from your Deleted Items and Junk E-mail folder as well as to delete old appointments and tasks.

To set up AutoArchive, right click on the folder you want to archive and choose Properties. Select the AutoArchive tab and configure the options.

For example, you may want to keep deleted and junk mail items for 3 days, then delete it. Choose "3" and "Days" for the Clean out items older than fields and select permanently delete.

Repeat this for each folder you want to delete messages from.

Be sure to open the Tools, Options, Other, AutoArchive dialog and set it to run every few days and your trash messages will be deleted automatically.