Ah... i got it... the 4 options were all set to '--'.
When I mapped them to the approprate folder it worked correctly... moved the mail to Trash, and deleted on exit.
HOWEVER, I have hundreds of users, and I guarantee I'll get dozens of calls about this. How can set these folder mappings to a default, so that the user doesn't have to set it up?
My config file has the 'drafts_mbox', "junk_mbox', 'sent_mbox', 'trash_mbox' all set to the appropriate folders, but evidently this doesn't set the defaults on this user configured section.