app.yaml

application: letsgateway
version: 1
runtime: python
api_version: 1

inbound_services:
- mail

handlers:
- url: /emails
  script: outgoing.py
  secure: always
- url: /_ah/mail/.+ 
  script: incoming.py 
  login: admin

incoming.py

from google.appengine.ext import webapp
from google.appengine.ext.webapp.mail_handlers import InboundMailHandler
from google.appengine.ext.webapp.util import run_wsgi_app
from google.appengine.api import urlfetch
import urllib

class MailHandler(InboundMailHandler):
  def receive(self, message):
    content_type, encoded = message.bodies(content_type='text/plain').next()
    body = encoded.decode()
    sender = message.sender
    subject = message.subject
    urlfetch.fetch("http://localhost:3000/emails/handle_incoming", urllib.urlencode({'body':body, 'sender':sender, 'subject':subject}), urlfetch.POST) 
    
application = webapp.WSGIApplication([MailHandler.mapping()], debug=True)

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

outgoing.py

from google.appengine.ext import webapp
from google.appengine.ext.webapp.util import run_wsgi_app
from google.appengine.api import mail

class OutgoingEmailHandler(webapp.RequestHandler):
  def post(self):
	message = mail.EmailMessage(sender="someone@somewhere.com")
	message.subject = self.request.get('subject')
	message.to = self.request.get('to')
	message.body = self.request.get('body')
	message.send()    
  
application = webapp.WSGIApplication([('/emails', OutgoingEmailHandler)], debug=True)

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