Sender Checks

I've configured my mailqueue using postfix and I'm now doing some header
checks to prevent forged from headers. However , I would like to do it
to all domains (not only from free mail servers like yahoo and hotmail).
Is this possible or do I have to add all domains do the list of domains
that need to be checked?
I'm using this config on main.cf:
smtpd_restriction_classes = from_freemail_host
from_freemail_host = check_client_access
hash:/etc/postfix/maps/freemail_hosts , reject

I need this because lots of UCE are still going through the mailqueue to
the main server... and all of them have forged from headers... (I've had
about 2000 messages accepted on my mailqueue and most of them were UCE).

thx
--
Pedro Macedo