The provider can be selected using the `provider` configuration value, or set in the [`providers` array using AlphaConfig](https://oauth2-proxy.github.io/oauth2-proxy/configuration/alpha-config#providers). However, [**the feature to implement multiple providers is not complete**](https://github.com/oauth2-proxy/oauth2-proxy/issues/926).
Please note that not all providers support all claims. The `preferred_username` claim is currently only supported by the
OpenID Connect provider.
## Email Authentication
To authorize a specific email-domain use `--email-domain=yourcompany.com`. To authorize individual email addresses use
`--authenticated-emails-file=/path/to/file` with one email per line. To authorize all email addresses use `--email-domain=*`.
## Adding a new Provider
Follow the examples in the [`providers` package](https://github.com/oauth2-proxy/oauth2-proxy/blob/master/providers/) to define a new
`Provider` instance. Add a new `case` to
[`providers.New()`](https://github.com/oauth2-proxy/oauth2-proxy/blob/master/providers/providers.go) to allow `oauth2-proxy` to use the
