When you create a user on the Server you must give that user a password. This is the password they will be required to enter to access their e-mail.
To change a User's password, go to the Users section (by clicking the
Users button from the main button bar), then click on the user whose password
you wish to change. You should now see your selected user in a User Configuration
Window. The second button in the Tool Bar has a picture of a user whispering .
Click on this button to change the user's password.