(1) some people were reporting a missing newline after the message
separator, which broke editing when there was not message signature. I haven't
been able to reproduce with the current mu4e, with either emacs 23 or 24,
but hopefully this helps
(2) don't kill send buffers (which may not work), bury them instead (let
message-mode handle this). To kill the buffers, set
message-kill-buffer-on-exit to t.
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