Drive-by debitrot. Tests pass. I make no guarantees.

package.mk

@@ -1,4 +1,4 @@
 RELEASABLE:=true
 APP_NAME:=rabbitmq_smtp_server
 DEPS:=rabbitmq-server rabbitmq-erlang-client erlang-smtp-wrapper
-TEST_SCRIPTS:=spec/run-specs.sh
+WITH_BROKER_TEST_SCRIPTS:=spec/run-specs.sh

src/rabbitmq_smtp_server.erl

@@ -110,7 +110,8 @@ deliver(Status, [Path | Rest], Message) ->
             case rabbit_basic:publish(
                    rabbit_basic:delivery(false, false, none,
                                          Message#basic_message{exchange_name = XName,
-                                                               routing_key = RK})) of
+                                                               routing_keys = [RK]},
+                                         undefined)) of
                 {ok, _, _} -> deliver(Status, Rest, Message);
                 _ -> deliver(one_or_more_deliveries_failed, Rest, Message)
             end;