Jani Nikula <jani@nikula.org> writes:
>
> By "sending from Gnus", do you mean exactly that, or do you mean
> notmuch-mua-new-mail which is basically some notmuch stuff layered on
> top of message-mode? If the latter, see M-x customize-variable
> notmuch-fcc-dirs. If the former, I'm wondering if we mess up
> message-mode somehow.
>

Hi Jani (and Bastien)

I can duplicate this with 

emacs -q 
M-x message-mail
ESC-ESC : (require 'notmuch)
M-x message-mail

so it does seem to be notmuch stomping on some message-mail
variable.

One workaround is to customize the variable notmuch-fcc-dirs to nil. 

I'm not sure if this behaviour is OK or not; the guilty function is
notmuch-fcc-initialization, notmuch-maildir.el