(define-key map "N" 'notmuch-show-next-message)
(define-key map "P" 'notmuch-show-previous-message)
(define-key map "n" 'notmuch-show-next-open-message)
(define-key map "N" 'notmuch-show-next-message)
(define-key map "P" 'notmuch-show-previous-message)
(define-key map "n" 'notmuch-show-next-open-message)