fix: update app engine standard mail sample to use the correct address format (#3096)

Co-authored-by: Leah E. Cole <[email protected]>

Author: chenyumic

appengine/standard/mail/attachment.py

@@ -21,7 +21,7 @@
 class AttachmentHandler(webapp2.RequestHandler):
     def post(self):
         f = self.request.POST['file']
-        mail.send_mail(sender='{}@appspot.gserviceaccount.com'.format(
+        mail.send_mail(sender='example@{}.appspotmail.com'.format(
             app_identity.get_application_id()),
                        to="Albert Johnson <[email protected]>",
                        subject="The doc you requested",

appengine/standard/mail/header.py

@@ -43,7 +43,7 @@ def get(self):
     def post(self):
         print(repr(self.request.POST))
         id = self.request.POST['thread_id']
-        send_example_mail('{}@appspot.gserviceaccount.com'.format(
+        send_example_mail('example@{}.appspotmail.com'.format(
             app_identity.get_application_id()), id)
         self.response.content_type = 'text/plain'
         self.response.write(

appengine/standard/mail/send_mail.py

@@ -37,7 +37,7 @@ def send_approved_mail(sender_address):
 
 class SendMailHandler(webapp2.RequestHandler):
     def get(self):
-        send_approved_mail('{}@appspot.gserviceaccount.com'.format(
+        send_approved_mail('example@{}.appspotmail.com'.format(
             app_identity.get_application_id()))
         self.response.content_type = 'text/plain'
         self.response.write('Sent an email to Albert.')

appengine/standard/mail/send_message.py

@@ -40,7 +40,7 @@ def send_approved_mail(sender_address):
 
 class SendMessageHandler(webapp2.RequestHandler):
     def get(self):
-        send_approved_mail('{}@appspot.gserviceaccount.com'.format(
+        send_approved_mail('example@{}.appspotmail.com'.format(
             app_identity.get_application_id()))
         self.response.content_type = 'text/plain'
         self.response.write('Sent an email message to Albert.')

appengine/standard/mail/user_signup.py

@@ -35,7 +35,7 @@ def post(self):
         else:
             confirmation_url = create_new_user_confirmation(user_address)
             sender_address = (
-                'Example.com Support <{}@appspot.gserviceaccount.com>'.format(
+                'Example.com Support <example@{}.appspotmail.com>'.format(
                     app_identity.get_application_id()))
             subject = 'Confirm your registration'
             body = """Thank you for creating an account!