Implement DNSBL checks (2)

Exim configuration
  deny message  = $dnslist_text
     dnslists = sbl.spamhaus.org:cbl.abuseat.org
...or...
warn  message = X-Warning: $sender_host_address is blacklisted at $dnslist_domain
  log_message   = found in $dnslist_domain
  dnslists = sbl.spamhaus.org:cbl.abuseat.org