I followed the above tutorial but using different version of postfix srpm ( version 2.4) with vda patch from http://postfix.wl0.org
I got the problem with quota.
When i set quota field in users table with default value '10485760', i got error message,
maildir delivery failed: user overdrawn his diskspace quota. Strangely, the user folder is empty.
I aslo try to manually create maildirsize with size of 10485760, but the problem still occured.
When i reset the value of quota field to 0, mail is delivered to user folder.
Any help is appreciated.