There's the /.well-known/browserid [1] file that can be used to delegate a domain to another identity provider.
The main thing is that while Persona talks about email verification, the protocol doesn't require that email handling exists. Just that a server vouches for the existence of a user@host, so using MX records wouldn't be 'correct' even if it would be a useful heuristic for google apps domains.
There has been talk of using SRV records, but it looks like the .well-known/browserid file will be the recommended way to do things.
The main thing is that while Persona talks about email verification, the protocol doesn't require that email handling exists. Just that a server vouches for the existence of a user@host, so using MX records wouldn't be 'correct' even if it would be a useful heuristic for google apps domains.
There has been talk of using SRV records, but it looks like the .well-known/browserid file will be the recommended way to do things.
[1] https://developer.mozilla.org/en-US/docs/Mozilla/Persona/.we...