Confirming email AFTER auto registration

There's nothing I'm sure of to do this, and not sure exactly what you're looking for. It sounds like you want email activation, which is something JFBConnect supports. However, it sounds like it doesn't matter if the user actually follows through with activation, which is a bit more confusing.

If they don't activate, I'm not sure what would happen.. eventually, are they deactivated?

One thing you could try is simply signing them up for a newsletter using Mailchimp or Sendy or something like that and verifying that the email doesn't bounce (or even sending an opt-in email).

I hope that helps give some ideas, but if not, or I'm not understanding properly, just let me know.

Thanks,
Alex