<i>&gt; With Persona, once you decide to login with your email account, first Persona looks for an IdP with your domain&#x2F;provider, the if not found it goes back to the persona catchall service.</i><p>This implies a classic chicken&#x2F;egg dilemma: email providers won&#x27;t implement Persona support unless that would be useful for lots of people; Persona wouldn&#x27;t be useful for lots of people until their email provider supported it.