[exim] Blacklist hostname/domain

Hi all,
I'm trying to blacklist a hostname, actually a reverse lookup on a IP
but I can't get this work.
so here the headers of the spam I receive :

Received: from bftp14.technical12.info ([92.222.251.69] 
helo=debian7.localdomain)
    by mx01.example.com with esmtp (Exim 4.82)

I wanna blacklist this "bftp14.technical12.info" actually
technical12.info. I tried to create an acl like this :

acl_smtp_blacklist_host:
         deny message = Sorry, your domain or address has been 
blacklisted by the admin.
         hosts = /etc/exim4/blacklisthosts.deny

But I doesn't work. Can you please help me ? I don't understand

thanks in advance,
Regards,

Bertrand Caplet