Comment 1 for bug 706649

We could use the Reply-By header, which is only used by Outlook as far as I can see but basically what we want. And it is mentioned in http://www.ietf.org/rfc/rfc2076.txt .

A calendar event is probably more compatible, though it feels clunky because I don't think it can actually say "reply needed" and it won't be associated with the message.

Maybe we want both.