Don't use the regular "'submit by email button." If you use this button,
you can only submit the data as XML. Instead, make your own button. In
the Object library under Standard objects, click and drag a plain button
to your form. Change the Control Type to Submit. Now you should have a
new tab called Submit with a "submit to URL" option. In that field type
the return email address in the following format:
mailto:jdoe@domain.com. Toward the bottom of the same option, there is a
field that says "...