Upon inspection of the RabbitMQ management UI I noticed that only some of the queues and exchanges have an _error queue/exchange defined.

After I threw an unhandled exception inside one of the consumers, which did not have an _error queue/exchange defined, I checked the RabbitMQ dashboard and found out that a new _error queue and exchange for the given message have been created.

This means that _error queues and exchanges are created when the first unhandled exception occurs and not during application startup.

If this is the normal behavior, I think it is worth to consider adding this information to the official MassTransit documentation.

If this is NOT the normal behavior, can you suggest any reasons why this might be happening?

Thanks!