I don't have Outlook 20007m but the settings will be close to the same.
In outlook 2003, Tools > Options > Mail Setup tab > click on Email accounts > view or change existing > highlight the correct mail account > change > more settings > Advanced tab, place check mark at LEAVE A COPY OF MESSAGES ON THE SERVER.
and you can also check REMOVE FROM SERVER WHEN DELETED FROM DELETED ITEMS FOLDER as suggested above |