[exim] Drop mail with some tld domain

I have problems of RAM amount on my server and have had to disable the
spamassassin.
Now I would want to block to all the mail that they arrive from
determines domains that end with TLD like .hu .ar .br .au .tw etc.
I have insert the follow line on acl_check_rcpt:

drop    message       = mail drop because $sender_address_domain is in
our blacklist / mail scartata perche\' $sender_address_domain e\'
presente nella nostra blacklist
          !senders      = lsearch;/etc/exim4/whitelist_mails.cfg
          sender_domains = lsearch;/etc/exim4/blacklist_domains.cfg

This rule works only when the domain is like example.com

In the file blacklist_domains.cfg I've insert the follow lines:

ar
br
hu
example.com
...
example.it

I've not found any example on the web or some function on the
exim-specific documentation that can help me to make it.

Andrea