def ready_to_send!
      identify_and_set_transfer_encoding
      parts.each do |part|
        part.transport_encoding = transport_encoding
        part.ready_to_send!
      end
      add_required_fields
    end
def ready_to_send!
      identify_and_set_transfer_encoding
      parts.each do |part|
        part.transport_encoding = transport_encoding
        part.ready_to_send!
      end
      add_required_fields
    end
Encodes the message, calls encode on all its parts, gets an email message
 ready to send