Hello All, I am having huge problems with an Exchange 2000 server that resides on an SBS 2000 server with all current SP's and hotfixes. None of the clients can open Outlook 2000 succesfully. However usual network access remains normal. The user double clicks on Outlook and then is constantly prompted to enter username, doamin and password. Even though these are correct the error message received is that you are not using the correct logon credentials. All exchange services have started correctly and the database does mount properly and is under 16Gb I am completely stuck. Please can you help. Dave.