aptitude versions php5 mysql-server postfix dovecot-imapd
Package dovecot-imapd:                      
i   1:1.2.15-7                                    stable                    500  
 
Package mysql-server:
p   5.1.49-3                                      stable                    500  
p   5.1.58-1~dotdeb.1                             stable                    500  
i   5.5.19-1~dotdeb.1                             stable                    500  
 
Package php5:
p   5.3.3-7+squeeze3                              stable                    500  
i   5.3.8-1~dotdeb.2                              stable                    500  
 
Package postfix:
i   2.7.1-1+squeeze1                              stable                    500  
p   2.8.3-1~bpo60+1                               squeeze-backports         100

dict {
  quotadict = mysql:/etc/dovecot/dovecot-dict-sql.conf
}
 
...
 
plugin{
  quota = dict:%u::proxy::quotadict
  quota_rule = *:storage=5G
}

driver = mysql
connect = host=127.0.0.1 dbname=postfix user=postfix password=trolololol
default_pass_scheme = CRAM-MD5
user_query = SELECT '/home/vmail/%d/%n/Maildir' AS home, 5000 AS uid, 5000 AS gid, CONCAT('*:bytes=', CAST(quota AS CHAR)) AS quota_rule FROM mailbox WHERE username = '%u' AND active='1'
password_query = SELECT password FROM mailbox WHERE username = '%u'

connect = host=127.0.0.1 dbname=postfix user=postfix password=trolololol
map {
  pattern = priv/quota/storage
  table = quota2
  username_field = username
  value_field = bytes
}
map {
  pattern = priv/quota/messages
  table = quota2
  username_field = username
  value_field = messages
}

virtual_mailbox_limit_maps = proxy:mysql:/etc/postfix/mysql_virtual_mailbox_limit_maps.cf
virtual_create_maildirsize = yes
virtual_mailbox_limit_override = yes
virtual_maildir_limit_message = Désolé, quota dépassé
virtual_overquota_bounce = yes

user            = postfix
password        = trolololol
hosts           = localhost
dbname          = postfix
query           = SELECT quota FROM mailbox WHERE username='%s' AND active = '1'

// Optional:
// Show used quotas from Dovecot dictionary backend in virtual
// mailbox listing.
// See: DOCUMENTATION/DOVECOT.txt
//      http://wiki.dovecot.org/Quota/Dict
//
$CONF['used_quotas'] = 'YES';
 
// if you use dovecot >= 1.2, set this to yes.
// Note about dovecot config: table "quota" is for 1.0 & 1.1, table "quota2" is for dovecot 1.2 and newer
$CONF['new_quota_table'] = 'YES';
 
 
// Default Domain Values
// Specify your default values below. Quota in MB.
$CONF['aliases'] = '50';
$CONF['mailboxes'] = '50';
$CONF['maxquota'] = '1024';
 
// Quota
// When you want to enforce quota for your mailbox users set this to 'YES'.
$CONF['quota'] = 'YES';
// You can either use '1024000' or '1048576'
$CONF['quota_multiplier'] = '102400';

virtual_alias_maps = proxy:mysql:/etc/postfix/mysql/mysql_virtual_alias_maps.cf
virtual_gid_maps = static:1029
virtual_mailbox_base = /data/virtual
virtual_mailbox_domains = proxy:mysql:/etc/postfix/mysql/mysql_virtual_domains_maps.cf
virtual_mailbox_maps = proxy:mysql:/etc/postfix/mysql/mysql_virtual_mailbox_maps.cf
virtual_mailbox_limit = 51200000
virtual_minimum_uid = 1029
virtual_transport = dovecot
virtual_uid_maps = static:1029

protocol imap {  
                login_executable = /usr/lib/dovecot/imap-login
                mail_executable = /usr/lib/dovecot/imap
                imap_max_line_length = 6553
                mail_plugins = quota imap_quota antispam
                }
 
protocol pop3 {  
                login_executable = /usr/lib/dovecot/pop3-login
                mail_executable = /usr/lib/dovecot/pop3
                mail_plugins = quota
                pop3_uidl_format = %08Xu%08Xv
                }

$CONF['used_quotas'] = 'YES';
 
// if you use dovecot >= 1.2, set this to yes.
// Note about dovecot config: table "quota" is for 1.0 & 1.1, table "quota2" is for dovecot 1.2 and newer
$CONF['new_quota_table'] = 'YES';