Today, Microsoft posted some much awaited information about the steps that will be necessary for Exchange Server, the Operating System, Windows Mobile, and Outlook clients. You can find it here:
The good news is that Windows Vista, Outlook 2007, and Exchange 2007 have the fixes in them.
The bad news is that chances are that you are not running any of those...
The good news is that if you are running Exchange 2003 SP2 you can get a fix... Soon.
The bad news is that if you are running Exchange 2003 SP1... you will need to go to SP2. Ok, that probably is good news.
But... If you have been holding off on installing some fixes because of the "Send As" changes, well... We updated the store.exe on this fix and it includes the "Send As" fix, so you are going to want to get your users configured correctly if you haven't yet already. See http://support.microsoft.com/kb/912918/en-us for more information.
I kid about this because it is going to probably hurt. I know that this will be somewhat painful for some of our larger customers. Fortunately, it looks like the product groups have done some good work in getting this information together. Please take a look at the first article for steps on how to make this as smooth as possible.