Permitir sólo a algunos emails acceder a la app en Rails

active_for_authentication.rb

# from http://www.rubydoc.info/github/plataformatec/devise/master/Devise/Models/Authenticatable

# Poner en el modelo User
def special_condition_is_valid?
  permitted_emails = [
    # Poner acá los emails permitidos para acceder
    "[email protected]",
    "[email protected]"
  ]
  if permitted_emails.include?(self.email)
    return true
  else
    return false
  end
end

def active_for_authentication?
  super && special_condition_is_valid?
end