We're trying to implement Windows Messenger using Exchange Server 2000 and are having an interesting problem. So far only four of us have had the service enabled in our user accounts and we've installed the appropriate Messenger programs on our PC's. When we run the program and tell it to use our Exchange server (in the Connect to Messaging Services window) we are asked for our Exchange email address. We put that in (which is actually our [email protected] instead of [email protected]) and we click OK. It logs us in no problem, but only two out of the four of us can chat with each other. The other two users can send us chat messages but we cannot reply. The message it give in the chat window is "The following message could not be delivered to all recipients". It's very strange and it's happening on one XP and one 2K PC. The two who work correctly are on 2K. Any ideas what might be wrong?