[exim] RBL Blocking

With a RBL you can block like this at RCPT time.

begin acl

deny
dnslists = bl.someblacklistthing.org
verify=recipient
message = SPAM: rejected because $sender_host_address is on
bl.someblacklistthing.org

What if I want to block at connect time like right after HELO, EHLO or
even before that?