If you wish to use email authentication, you must configure your Rails application to send email. Read here for more information.

I recommend using mailcatcher for development.

mailcatcher development example configuration:

# config/environments/development.rb
Rails.application.configure do
  config.action_mailer.default_url_options = { host: 'your-dev-host.dev' }
  config.action_mailer.delivery_method = :smtp
  config.action_mailer.smtp_settings = { address: 'your-dev-host.dev', port: 1025 }
end

If you wish to send custom e-mails instead of using the default devise templates, you can do that too.