What about domain names? Emails are bound to a domain name by definition, and indeed domain name IS designed as a good identity and can be used to host an email. See how domain names are owned by large corporations and trusted since day one and never lost, as long as you keep it carefully. It requires WHOIS information as the authoritative information of domain owner. An account based on username and password is what you usually need to access it, but if you are serious you can always choose a domain registar that is serious about keeping your domain name. It’s not free but it costs nuts compared to the cost of losing it, and let’s not forget that there is a cost behind hosting emails even if it’s given for free.