Event Reliability

[This is preliminary documentation and subject to change.]

Both synchronous and asynchronous events are reliable under normal conditions. That is, no sink notification will be skipped on an event. However Exchange may call a sink multiple times if there is a failure in the store. For example, the Exchange sink service may fail after three of five registered sinks have already been called. When the service comes back up, the three previously called sinks may or may not be invoked a second time. A sink that fails after being notified will not be notified again for that event.