We are using a forward to a friend link in one of our email invites for a webinar. If they register for the webinar they get an autoresponder email with an "add to outlook Calendar" (ics) file, and a confirmation of their registration.
Be aware that when the email is forwarded to a friend, the 'friend' is marked as unsubscribed. if the 'friend' registers for the webinar, they won't get the auto responder because they have been marked as unsubscribed.
Just thought I'd throw this out there as it caused an entire day of frustrating testing! Hope it helps someone out there!