What's the state of the art in sending lightly formatting e-mail in HTML format? Is org-mime still the best way?

This doesn't seem to be working for me. I'm doing this:

(setq load-path (cons "~/org/contrib" load-path))

(setq load-path (cons "~/org/contrib/lisp" load-path))

and this:

(require 'org-mime)

but when I call org-mime-subtree, I get this:

Symbol's function is void: org-export-string

(For reference: OSX 10.9.1 / Aquamacs 2.5 / Emacs 23.4.1 / org-mode 8.2.4