(use-modules (mailutils mailutils))

(define mbox (mu-mailbox-open "~/Mail/testmbox" "r"))

(define (get-messages mbox a b)
  (map (lambda (n)
	 (mu-mailbox-get-message mbox n))
       (map (lambda (n)
	      (+ a n))
	    (iota (+ (- b a) 1)))))

(let loop ((start 1)
	   (end 10))
  (when (< end (mu-mailbox-messages-count mbox))
    (let ((msgs (get-messages mbox start end)))
      (loop (1+ start)
	    (1+ end)))))