Help with postfix

I need help with postfix. I have a mail server installed on suse 11.1 and configured to receive email from my isp. Initially users where configured on the server and outlook could log in with there credentials and pick mail that was stored there. The system hard drive crashed and a new installation had to be done. Postfix has been installed now i am wondering how to go about with the business of configuring users to access mail because whenever i use outlook it say

“There was a problem loggin onto you mail server. Your Username or Password was rejected. Server response:’-ERR login failed.’.”

How do i configure the user to be authenticated and login onto the server using outlook?

Best regards

Please don’t double post. Mods, please move the other thread here.