def normalize!
      @domain.downcase!
      provider.modifications.each { |m| self.send(m) if self.respond_to?(m) }
    end
def normalize!
      @domain.downcase!
      provider.modifications.each { |m| self.send(m) if self.respond_to?(m) }
    end
Internal: Normalize email address according to rules specified by the provider

 Returns nothing