Please don't mark this as a duplicate [it is not]. If we had a complete answer to this question, we wouldn't have so many people asking related but differing questions about emailing, account signup, etc. We need a complete tutorial on how to make account signup scenarios work for both GAE standard and flexible environments.
What is the best way to implement signup email confirmation using django-allauth on Google App Engine flexible environment? This seems to be a glaring hole in Google App Engine documentation.
After reading tens of articles, each with a piece or two (sometimes incompatible) information, and wasting time, we are still left not know why our setup is not working. Judging by the amount of questions relating to this issue on Stackoverflow, I would recommend either this tutorial or GAE sample projects dealing with account signup and email confirmation.
We would like to see a complete tutorial also include other third party email options on GAE--like SendGrid, Mailgun or Mail-jet--for both GAE standard and flexible environments.