We're having a mishmash of issues that I cannot pin down and we're trying to solve. I'm treating this as a clean slate approach and not ruling out anything I've looked at before (so assume I haven't).
Some clients (but not all) are experiencing periodic issues within outlook. Most our users issues come when they are sending an email, selecting a new email to read, or moving a message between folders the client will freeze. That's the extent that many of these users report issues. A small subset of these users also have an issue where when this occurs that they get a message that says "Outlook is trying to retrieve data from the Microsoft Exchange Server (internal CAS server). One user specifically has an issue that, on occasion, when she receives a calendar invite and accepts or declines it, her outlook client will lock up and may or may not display the message.
I've managed to make some dents in the issue, but it's still persisting so I'm trying to figure out approaching from scratch where I need to look and what I need to tweak. All help is sincerely appreciated as according to our user survey Exchange is more important that the system that runs payroll :)