The title may be misleading. But this is something that I think would be great and I would happily pay for. There should be a website, or app etc, which allows you to type in your e-mail, then the website/app will look up everything that e-mail is linked with. Of course you would have to prove this is your email, perhaps, ironically, from sending a verification email to a separate email. The whole idea is that people can see what they're account is linked with. For example an old facebook a
in The Open Castle Inn