[Exim] Blocking on sending e-mail

Hi,

I've installed version 4.01 and in my configuration file I've added a
RBL filter in the ACL configuration part:

  warn    message       = X-RBL: $sender_host_address is in a black list
at $dnslist_domain
          log_message   = found in $dnslist_domain
          dnslists      = inputs.orbz.org

It works fine most of the time, however sometime my DNS server is not
working properly and nslookup on 2.0.0.127.inputs.orbz.org fails after a
long time, then exim is not able to send email. Here is the typical
session:

220 pompeii.ise ESMTP Exim 4.01 Thu, 21 Mar 2002 19:47:33 -0800
mail from: my_email_address@my_domain.com
250 OK
rcpt to: address@???

And it is blocked at checking `address@???' which is a valid
email address as well as the sender address which is a local one.

Is there something I could do so that exim is able to send email without
checking for RBL when it comes from inside?

Thanks,
Manu