outlook might be having troubles finding the exchange servers. what happens
if you add the exchange server(s) and ip address(es) to your local
host/lmhosts files? (Oh, if you are not running in cached mode and you are
prone to get lots of attachments and use the new preview pane, it looks like
outlook is roundtripping the server to bring the attachments down in order
to display the message. i find running in cached mode seems to help along
with disabling any av software that scans mail, instant messenger
integration, and the reformatting of plain text messages.)