Sorry to disagree, but changing the form will only work if you send mail to a person that has the same form design, unless you also send the design with the form (stored-form). But the recipient still has the option not to accept stored-form documents, and if the recipient does not have Notes, it is entirely useless to do so.
For sending mail outside the company, by definition that means it will not work.
The only way to do it is therefore by including in the Body field, as Dominik has indicated.