This sounds like something else. In the outlook case their servers they seem to use the connection as a stream (which is actually valid, although not really sup

This sounds like something else. In the outlook case their servers they seem to use the connection as a stream (which is actually valid, although not really supported by browsers outside of the event-stream class), where the server only writes little chunks of data of a time. But the server there not hindered from writing by a slow client - it simply has not more data to write at that point of time.