So, without further ado, here comes the naked code:
<form method="post" action="mailto:firstname.lastname@example.org">
<p>Will you attend?<br />
<input type="radio" name="will_attend"> Sure!<br />
<input type="radio" name="will_attend">Maybe?<br />
<input type="radio" name="will_attend">Nope.<br />
The problem now is to get this code into a message you create in an email program. To do so, you have to look for a way to edit the HTML source to the message. Unfortunately, this is not always possible. Outlook Express 5 for Macintosh for example offers no way to edit it; neither does Eudora. Netscape and well as Mozilla offer a way to insert HTML tags into the message. It's not perfect, but it works.
There, you can edit freely and insert the form code as you like. Once you are done with both entering the form source code and writing the rest of the message, you can send it — and have sent a form via email, something only very few have done so far!
In response, you will (hopefully) receive the results of the form in raw data form, which you will have to post-process, just as you would if the email form was on a page on the Web. Of course, you will only get results at all if the recipients of your emailed form can display HTML in their email clients.