Diagnostic-Code: X-Postfix; unknown user: ( after deleting a mailinglist and create normal account )

Hi there,

Got a little issue i do not get resolved. Hope you can help..
Setting up ISPConfig was easy, but ran into the following.

I had a domain setup with several users / aliasses and mailinglists. all worked fine..
then deleted a mailinglist and instead created a normal account . But this account does not want to recieve mails.
I can log in to roundcube with this user. I can see the vmail dir for the user gets created..
All other accounts work fine, if i create a new account with different name it works fine..
just this one which has been a mailinglist does not want to recieve mails it seems

Hope anyone can give me some direction where to look..

error i can see is:
Action: failed
Status: 5.1.1
Diagnostic-Code: X-Postfix; unknown user: "<username>"