BrowserID works by default with email but it has absolutely to dependency on email. It uses it for namespacing and bootstrapping, but nothing else.<p>So foo@bar.com may or may not have any MX records, all that is required is that bar.com can provide an assertion that you control foo@bar.com.<p>The way bar.com determines that is entirely up to bar.com, it can be a password, smart crypto card, local kerberos or Windows auth, 3-way auth involving your cat Rufus, etc...<p><a href="https:&#x2F;&#x2F;developer.mozilla.org&#x2F;en-US&#x2F;Persona&#x2F;Protocol_Overview" rel="nofollow">https:&#x2F;&#x2F;developer.mozilla.org&#x2F;en-US&#x2F;Persona&#x2F;Protocol_Overvie...</a>