https://cloud.google.com/appengine/docs/python/release-notes
> Google no longer accepts quota increase requests for the mail service. Customers should use Sendgrid instead. Google will probably deprecate it soon, and close it a year later. -- You received this message because you are subscribed to the Google Groups "Google App Engine" group. To unsubscribe from this group and stop receiving emails from it, send an email to google-appengine+unsubscr...@googlegroups.com. To post to this group, send email to google-appengine@googlegroups.com. Visit this group at https://groups.google.com/group/google-appengine. To view this discussion on the web visit https://groups.google.com/d/msgid/google-appengine/7956feaf-8501-429f-bb05-4067662ba49c%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.