AS3 Email with subject and body

[darngooddesign]

shareBtn.addEventListener(MouseEvent.CLICK, onShare);
function onShare(event: MouseEvent) {
var request:URLRequest = new URLRequest("mailto:emaila address"+"?subject=Subject of email"+"?body=Body of email);
navigateToURL(request, "_self");
}

I'm trying to populate all the fields of an email, but I can only send info to two of them. If I send all three pieces of info the Subject ends up "Subject of email?body=Body of email", but if I ditch either the subject or body the other fields populate correctly. Any ideas why all three can't be populated?

Cheers