mh-thread-ancestor
mh-thread-ancestor is an interactive autoloaded Lisp function in `mh-thread.el
'.
(mh-thread-ancestor &optional THREAD-ROOT-FLAG)
Display ancestor of current message.
If you do not care for the way a particular thread has turned,
you can move up the chain of messages with this command. This
command can also take a prefix argument THREAD-ROOT-FLAG to jump
to the message that started everything.