anchor.diff:          [] -> {ok, notlisted};
           _ -> {ok, {blocked, DNSBL}}
       end.
  +
  +%% @doc Default list of DNSWL services
  +dnswl_list() ->
  +    [
  +        "list.dnswl.org",       % https://www.dnswl.org/?page_id=15
  +        "swl.spamhaus.org"      % http://www.spamhauswhitelist.com/en/usage.html
  +    ].
   
   %% @doc Default list of DNSBL services
   dnsbl_list() ->
  
positive.code:     {ok, notlisted};
  check_addr_list(DNSBL, List) ->
      List1 = lists:filter(fun
                              ({127,0,0,_}) -> true;
                              (_) -> false
                           end,
                           List),
  
negative.code: -export([
      is_blocked/1,
      is_blocked/2,
      is_blocked/3,
      status/1,
      status/2,
      status/3,
      dnswl_list/0,
      dnsbl_list/0,
  
      test/0
  