Infinite retries and potential log entries lost upon delivery failure

[JayBeavers]

Describe the problem to solve
My quick read of MessageTransmitter is that undelivered messages will infinitely queue in RAM as SendMessageAsync recursively calls itself upon delivery failure. This would mean that queues build up to memory exhaustion and pending messages are lost on process exit if I'm reading it correctly.

Describe the feature proposed
It would be beneficial to adopt a retry mechanism, potentially with an exponential backoff delay, which is triggered by delivery issues. This target could also use a size and time limited local file system persistence store for messages which were not delivered, so that they can be transmitted when there are no more delivery issues.

[luigiberrettini]

Closing this issue after split.

[JayBeavers]

Thank you. Good call splitting into two items.