This may sound paradoxical, but Persona has nothing to do with actual email. Well, except for Mozilla-provided fallback/compatibility authenticator that, indeed

This may sound paradoxical, but Persona has nothing to do with actual email. Well, except for Mozilla-provided fallback/compatibility authenticator that, indeed, uses actual email. It just a protocol that - oversimplifying things - allows a certain server (identified by domain name) to issue you a certificate that says that you have a name associated with that server. It's usually an email, but can be anything that could be represented as (name, domain) pair by concatenating those with "@" character. For example, XMPP ID, forum nickname or system account.