Originally Posted by till
The fix is to remove irtual_mailbox_limit_maps line in postfix main.cf and restart postfix. Quota is handled by the LDA (courier maildrop or dovecot deliver) in a ispconfig 3 setup. I've fixed that in SVN.
What i've noticed is that dovecot has the maildirsize file and if you increase the quota, nothing resets the header sized value in that file and the user is still limited to the original size for some reason..
RETRACK that comment. left overs of courier..