Anyone know if this is possible? Is there a 3rd party app out there to provide this functionality? I've got some crazy users who would like to have it

What i'm referring to is.. in Outlook, it automatically saves a cache of all email addresses that you send to.. whether or not they are contacts within your address book. When you go to compose a new email in Outlook, you can start typing and pull up the old addresses from the cache. This cache is stored in Outlook's NK2 file.

On BlackBerry, when you compose an email.. it auto-completes based on contacts in your address book.. but doesnt seem to keep track of email addresses that are typed in manually (not added into a contact).