An important point to note is that WebDAV is not available in Exchange 2010 and hence previous versions of entourage will not be able to connect the way they used to. This becomes a huge barrier for companies who have a large Mac estate (like media companies) to migrate to exchange 2010. In this case, upgrading exchange to 2010 will have to be combined with upgrading all entourage clients to the latest version.
The only other possible connections using entourage which doesn’t support Exchange Web Services (EWS) will be POP or IMAP, provided that they are enabled in your network. Only entourage versions which support exchange web services will be able to successfully connect to exchange, making use of the autodiscover functionality.
Microsoft has dropped WebDAV in Exchange 2010, replacing it with Exchange Web Services (EWS), which it says will support more exchange capabilities. A new email client named “Outlook For Mac” will be released next year replacing the latest entourage 2008. It is expected to give the same look and feel like Outlook for windows & improve the user experience.