(define-key map (kbd "<backtab>") (notmuch-tree-to-message-pane #'notmuch-show-previous-button))
(define-key map (kbd "TAB") (notmuch-tree-to-message-pane #'notmuch-show-next-button))
(define-key map "e" (notmuch-tree-to-message-pane #'notmuch-tree-button-activate))
(define-key map (kbd "<backtab>") (notmuch-tree-to-message-pane #'notmuch-show-previous-button))
(define-key map (kbd "TAB") (notmuch-tree-to-message-pane #'notmuch-show-next-button))
(define-key map "e" (notmuch-tree-to-message-pane #'notmuch-tree-button-activate))