If you insert the unsuitable characters in a mail message, Emacs
behaves a bit differently. It additionally checks whether the
most-preferred coding system is recommended for use in MIME messages;
-if it isn't, Emacs tells you that the most-preferred coding system is
+if not, Emacs tells you that the most-preferred coding system is
not recommended and prompts you for another coding system. This is so
you won't inadvertently send a message encoded in a way that your
recipient's mail software will have difficulty decoding. (If you do