There’s lots of opportunities to induce a service to send an email to an arbitrary address — e.g: I sign up for a LinkedIn account with your email address — so

There’s lots of opportunities to induce a service to send an email to an arbitrary address — e.g: I sign up for a LinkedIn account with your email address — so there’s a few common patterns that could be used. For example, the first time an email address is seen by the service as a “send me a copy” address, the service could first send a confirmation email (much like a “did you register for a LinkedIn account?” confirmation email) before sending a copy of the message. Framed as a feature (i.e: subscribe to receive a copy of any message sent from your address) it could be quite compelling! I’d love to know what people are claiming I sent via message forms (how valuable it would be, I don’t know, but it’s certainly something I’d sign up for).