When I reply to an emailed invitation, it should do something useful

(User Story, Investigate , Priority: High, Test Status: No automated tests yet , Reported By Justin du Coeur, )
Email, Invites
Summary: Currently, invitations to Spaces come from "userEmails@querki.net" -- which means that all replies go to me, personally. This is bad.
For the short term, these emails should be marked clearly as "do not reply" -- the invite might come from, eg, "Justin du Coeur (do not reply) <noreply@querki.net>", so that at least we aren't fooling people inadvertently, and so they're not sending potentially personal emails to me. Once that is done, downgrade this to High.
In the medium term, we should set up an email inbox mechanism, whereby the From address comes from a one-shot, signed address that can be parsed and routed as a Notification.