Plesk 11.x / Linux :: Postfix Smtp Delay

I've a problem with a server with Postfix. Emails (smtp) are refused by an operator because there is too many mail sent in a few moment.

With Qmail, we make this config :

1) we create file concurrencyremote
# vi /var/qmail/control/concurrencyremote
with the value 3

2) we restart Qmail and it's ok

With Postfix, we make that :

1) we modify the file /etc/postfix/main.cf
default_destination_concurrency_limit = 3

2) In /etc/postfix/transport :
wanadoo.com slow ;
wanadoo.fr slow ;
orange.fr slow ;
orange.com slow ;
laposte.net slow ;
.wanadoo.com slow ;
.wanadoo.fr slow ;
.orange.fr slow ;
.orange.com slow ;

3) After :
#postmap /etc/postfix/transport

4) In /etc/postfix/master.cf :
slow unix - - n - 5 smtp -o syslog_name=postfix-slow -o smtp_destination_concurrency_limit=3 -o slow_destination_rate_delay=1

5) In /etc/postfix/main.cf :
slow_destination_recipient_limit = 20
slow_destination_concurrency_limit = 3

And we modify :
transport_maps = hash:/var/spool/postfix/plesk/transport, hash:/etc/postfix/transport

6) At the end :
# /etc/init.d/postfix reload

But it doesn't work. Operator "Orange" refused emails.

In maillog, we have :
dsn=4.3.0, status=deferred (mail transport unavailable)