I found a couple of POP connectors, but non that both downloads and sends emails. If that's at all possible.
I'd like to explore the possibility of using exchange as the local mailbox store only, but not handle the sending or receiving. I know it might seem like it defeats the purpose, but as a contingency measure it can turn out to be useful.
You can setup Google Apps as your primary MX handler, taking advantange of: great antispam filter, best I've seen so far, large storage capacity, and most importantly it's FREE service. Have a pop/smtp connector manage the traffic to/from the exchange server.
What do you experts think?