How good is message threading?
Threading usually works very well, but occasionally there is a hiccup. For example, one might see two different topics threaded together. Usually this occurs when a message author hits reply to a message in one topic, but manually changes the subject line to match another topic. When this happens, the threading subsystem has to decide whether to track “who replied to what”, or to track the subject line. The Mail Archive goes with the former because that is usually more reliable. For more information about threading and the special email headers that get inserted into a message whenever you hit reply, see the MHonArc FAQ entry.
