The best strategy is usually to tell the sender that their message could not be delivered and let them decide how to deal with this. Unfortunately, most current

The best strategy is usually to tell the sender that their message could not be delivered and let them decide how to deal with this. Unfortunately, most current message queue systems are not end-to-end (e.g. re-send or modify their message); they usually have an additional intermediate service like HTTP or a WebSocket API to interface with end users; this design makes it difficult to implement this kind of error-routing mechanism, especially at scale when different end users might be connected to different hosts.