We have Windows 98 clients that could not connect to Exchange Instant Messaging. Their client software repeatedly asked for authentication even though user/email and password are entered correctly. The client software for Directory Services are already installed on their machines. Even changing how they log-on to the client software (user@xxxxxxxxxx to user@xxxxxxxxxxxxxxxxx) are unsuccessful. Windows 2000 clients can connect the the Exchange Instant Messaging. I would appreciate your advise and suggestion on how to resolve this problem. Thank you.