Problem defining incoming mail settings

Hello,

We have created an ActiveDirectory account (Exchange 2000) especially for Service Desk ; but when entering the login info in incoming mail settings, we've got the error message "FAILURE :Email Settings saved successfully. But error occured while trying to check connection with mail server - Authentication Failed using the given username and password."

Curiously, after some more tries, it appears that old accounts (first created in NT network and imported in Exchange 2000 during its installation) are working without any problem ; only the accounts directly created under Exchange 2000 don't work... and it's impossible for us to figure out which difference existst between the two types of accounts !

Has someone got an idea ? Thanks in advance...

Olivier