First, let me say that i think this is purely and outlook issue. I have posted this on the outlook forums without much of a response. I'm hoping some here has another idea.
Basically, i have users who work in cached mode (not optional) and send-as certain mail enabled public folder. This tends to break often for them and they receive a bounce back message saying that they do not have rights. Usually deleting the auto populating address from the "from" field fixes this. That being said, this has to be done way to often and sometimes a profile recreation is needed as well.
Below is my original post. Thanks.