Messages do not get audited with outbox enabled

[agiudici]

Symptoms

The messages do not get audited.

Who's affected

Anyone using the Outbox feature.

Original issue

We are using RabbitMQ transport and the Outbox feature, but when outbox is enabled we stop receiving messages in the audit queue.

Our config is:
configuration.UseTransport();
configuration.EnableOutbox();
configuration.UsePersistence()
.For(Storage.Outbox, Storage.Sagas, Storage.Timeouts, Storage.Subscriptions, Storage.GatewayDeduplication);

When me comment out the line that enable the outbox, the audit messages start again.

Is there any other configuration that we should set?