More on Email to URL discovery

Just a couple more thoughts on this topic.

1. I believe that the mapping from email domain to XRDS URL should include some addition pattern to make deployments easier. Deploying a servlet or other mechanism on the root email domain is not always easy. Having a different pattern such as xrds.my-email-service.domain would simplify deployment issues.
2. While it is nice that an email to URL mapping service can provide user-centric identifier management, I don't know how much it will be used by the general public. Discovering that the email provider is also an OpenID 2.0 provider would be enough to start a directed identity flow. This I believe would be more convenient for most users.