In V6 there is a new setting, questionably a "feature".
I picked up this piece of information at ACUC, and it was the first thing I set after I installed V6.
You must go to Edit-My preferences-User preferences. There is a setting, "Automatically clear 'Deleted Message' box when logging out". By default, it is unchecked. You must go in and check it for each user in order to clear the messages.
