Receiving Mail in Google App Engine

Question

I am reading the tutorial about Receiving Mail. I updated the app.yaml file as instructed:

application: hello-1-world
version: 1
runtime: python
api_version: 1

handlers:
- url: /favicon.ico
  static_files: static/images/favicon.ico
  upload: static/images/favicon.ico

- url: /_ah/mail/.+
  script: handle_incoming_email.py 
  login: admin

- url: /.*
  script: hw.py

inbound_services:
- mail

And created a handle_incoming_email.py

import cgi
import os
import logging
from google.appengine.api import users
from google.appengine.ext import webapp
from google.appengine.ext.webapp.util import run_wsgi_app
from google.appengine.ext import db
from google.appengine.api import mail
from google.appengine.ext.webapp.mail_handlers import InboundMailHandler

class ReceiveEmail(InboundMailHandler):
    def receive(self,message):
        logging.info("Received email from %s" % message.sender)
        plaintext = message.bodies(content_type='text/plain')
        for text in plaintext:
            txtmsg = ""
            txtmsg = text[1].decode()
            logging.info("Body is %s" % txtmsg)
            self.response.out.write(txtmsg)

application = webapp.WSGIApplication([
  ReceiveEmail.mapping()
], debug=True)

def main():
    run_wsgi_app(application)
if __name__ == "__main__":
    main()

I also have hw.py that I used to practice sending email. That one works.

Now I go to http://localhost:8081/_ah/admin/inboundmail and send an email to [e-mail]

Can anyone explain to me how I process this email? How do I access the content of the email? I have the code

self.response.out.write(txtmsg)

in handle_incoming_email.py but that does not print anything.

I would greatly appreciate if someone clarify how receiving email works.

For instance, in this question

class MailHandler (InboundMailHandler):
  def receive(self, message):
    sender = message.sender
    user_account = db.GqlQuery("SELECT * FROM Task WHERE user = :1", sender).fetch(5)

as far as I understand sender is the email of the sender. So, in my case, how do I access the sender email address.

Also, why do I need to have a separate script to handle incoming mail? Why can't I put the ReceiveEmail handler in my hw.py script? If I do that, where do I put the line

application = webapp.WSGIApplication([
  ReceiveEmail.mapping()
], debug=True)

I would be grateful if you can help me with these questions.

(I asked the same question in GAE group but there were no answers.)

Answer 1

Is [e-mail] a valid google user? GAE can receive/send mails only from the google user of your application. Your code seems correct.

"Also, why do I need to have a separate script to handle incoming mail? Why can't I put the ReceiveEmail handler in my hw.py" -> the main script is to handle url request, I think is much clearer in this way.