driver = mysql
connect = host=localhost dbname=postfixadmin user=dovecot password=xxxxxxxx
default_pass_scheme = MD5-CRYPT

password_query = \ 
  SELECT username, domain, password \ 
  FROM mailbox WHERE username = '%u' AND active = 1

user_query = \ 
  SELECT username AS user, \
         'vmail' AS uid, \  
         'vmail' AS gid, \  
         '/var/vmail/%u' AS home, \
         CONCAT('*:bytes=', CAST(quota AS CHAR)) AS quota_rule \
  FROM mailbox WHERE username = '%u' AND active = 1