(define-key map (kbd "<C-tab>") 'widget-backward)
(define-key map (kbd "M-TAB") 'notmuch-show-previous-button)
(define-key map (kbd "<backtab>") 'notmuch-show-previous-button)
(define-key map (kbd "TAB") 'notmuch-show-next-button)
(define-key map (kbd "<C-tab>") 'widget-backward)
(define-key map (kbd "M-TAB") 'notmuch-show-previous-button)
(define-key map (kbd "<backtab>") 'notmuch-show-previous-button)
(define-key map (kbd "TAB") 'notmuch-show-next-button)