Can't login to webmail

[OnTheRun]

Hello all,
thanks for developping such a great system. I just love it!
I set up ispconfig on debian 3.1. Most of the things went without problems, not so the email.
I thought I'd test it first with an account on some domain. So I created a user (web7_user i.E.) and gave him a password. I then tried to login into ftp, which went without any problem. But when I try to log onto webmail (using UebiMiau) I always get the message: You cannot login with the username and password entered.
I used exactly the same logins as for the ftp (web7_user, 123456). In /var/log/mail.log I get:

Nov 30 21:18:53 myserver courierpop3login: Connection, ip=[::ffff:127.0.0.1]

What could be the problem here?
Everything else is working just fine
Is it possible to have a system running with virutal users and domains with postfix, courier and mysql (like explained on http://howtoforge.com/virtual_postfi..._quota_courier) but to generate the accounts in ispconfig (like i'm now doing it at the users&email-tab)?

Thank you and with kind regards