[Dovecot] Overwriting user Quota

[Thomas Krause]

Dear List,
I cannot overwrite the default quota. In dovecot.conf I have

plugin {
  quota = maildir:User quota
  quota = dict:user::proxy::quotadict
  quota_rule = *:storage=380M:messages=10000
  quota_rule2 = Trash:storage=100M
} 

To overwrite, I put in dovecot-sql.conf

user_query = SELECT CONCAT('/vmail/', maildir) AS home, \
 CONCAT('maildir:/vmail/', maildir) as mail, \
 CONCAT('*:bytes=', quota) AS quota_rule \
 FROM mailbox WHERE username = '%u' AND active = '1'

Debugging dovecot:

imap-login: Login: user=<x at y.z>, method=PLAIN, rip=a.b.c.d, lip=e.f.g.h
IMAP(x at y.z): Loading modules from directory: /usr/local/lib/dovecot/imap
IMAP(x at y.z): Module loaded:
/usr/local/lib/dovecot/imap/lib10_quota_plugin.so
IMAP(x at y.z): Module loaded:
/usr/local/lib/dovecot/imap/lib11_imap_quota_plugin.so
IMAP(x at y.z): Effective uid=101, gid=6, home=/vmail/x.z/x/
IMAP(x at y.z): Quota root: name=user backend=dict args=:proxy::quotadict
IMAP(x at y.z): dict quota: user=x at y.z, uri=proxy::quotadict, noenforcing=0
IMAP(x at y.z): Quota rule: root=user mailbox=* bytes=398458880 messages=10000
IMAP(x at y.z): Quota rule: root=user mailbox=Trash bytes=104857600 messages=0
IMAP(x at y.z): Namespace: type=private, prefix=INBOX., sep=., inbox=yes,
hidden=no, list=yes
, subscriptions=yes

mysql> select CONCAT('*:bytes=', quota) AS quota_rule FROM mailbox  where
username="x at y.z" and active=1;
+-------------------+
| quota_rule        |
+-------------------+
| *:bytes=800000000 | 
+-------------------+
1 row in set (0.00 sec)

What is my mistake? I'm using dovecot 1.1.11

Best regards,
Thomas.