You can do something like this:
Form:
<p>Radio Button 1 [radio radio-1 "Item 1" "Item 2" "Item 3"]</p>
<p>Radio Button 2 [radio radio-2 "Item 1" "Item 2" "Item 3"]</p>
<p>Radio Button 3 [radio radio-3 "Item 1" "Item 2" "Item 3"]</p>
<p>[submit "Send"]</p>
Mail: Message body
Radio Button 1: [radio-1]
Radio Button 2: [radio-2]
Radio Button 3: [radio-3]
For more info on using Radio Buttons - see http://www.quackit.com/html/codes/html_radio_button.cfm