Q&A: Can I use Entourage for Web Services with Exchange 2003?

I've seen a few variations of this question lately:

Is EWS Exchange 2007 only? Will it work with 2003 just with no benefits or does it simply not integrate?

Here's the short answer: Entourage for Web Services will only work with Exchange 2007 or later. If you're using Exchange 2003, Entourage for Web Services will not work. If you're only using Entourage to connect to a POP (such as Hotmail) or IMAP (such as MobileMe) account and you're not connecting to an Exchange account at all, you can use either version of Entourage, but there's no compelling reason to use Entourage for Web Services. And if you don't care about gory technical details, you can skip the rest of this post.

Through Entourage 2008, WebDAV has been our primary method to communicate with your Exchange server. Exchange 2007 introduced a new API: Exchange Web Services. In Entourage 2008, we added some features using Exchange Web Services instead of using WebDAV. Our out-of-office (OOF) assistant uses Exchange Web Services if you're on an Exchange 2007 server, for example. In Exchange 2010, which is in public beta now, WebDAV isn't included at all.

Support of Exchange Web Services brings us a lot of goodness. It's blazingly fast, and it gives us access to Exchange features that we couldn't support earlier. Synchronising categories, notes, and tasks have all been highly-requested features, and moving to Exchange Web Services made it possible for us to fulfill those requests.

In Entourage for Web Services, we pulled out all of our old WebDAV code and replaced it all with shiny new Exchange Web Services code. Since that old WebDAV code is gone, Entourage for Web Services can't talk to an Exchange 2003 server at all. The future is Exchange Web Services, and we're already there.