[exim] backup of incoming mail, two deliveries

Hello.

I am trying to setup a backup of all incoming mail for safety. It works
well, except that the backup mails are delivered twice, as this log
shows:

2004-12-16 12:05:35 1CetRr-0002fA-00 => kowalski <kowalski@???>
D=procmail T=procmail_pipe
2004-12-16 12:05:35 1CetRr-0002fA-00 => kowalski <kowalski@???>
D=backup_router T=backup_delivery
2004-12-16 12:05:35 1CetRr-0002fA-00 => kowalski <kowalski@???>
D=backup_router T=backup_delivery
2004-12-16 12:05:35 1CetRr-0002fA-00 Completed

The server is Debian GNU/Linux stable, with exim 3.35.

I defined the following transport:

backup_delivery:
driver = appendfile
user = cyrus
group = cyrus
envelope_to_add
return_path_add
prefix = ""
directory = /var/mailbackup/${local_part}
maildir_format
create_directory
current_directory = /


In the directors, before existing ones, I added:

backup_router:
driver = localuser
transport = backup_delivery
unseen = true



Any tips ?

Thanks.

--
Nicolas