diff --git a/appengine/standard_python3/bundled-services/blobstore/django/main.py b/appengine/standard_python3/bundled-services/blobstore/django/main.py
index 8587852c9935..3840bc5ec479 100644
--- a/appengine/standard_python3/bundled-services/blobstore/django/main.py
+++ b/appengine/standard_python3/bundled-services/blobstore/django/main.py
@@ -56,6 +56,8 @@ def get(self, environ, photo_key):
             # GAE sets it to a guessed type if the header is not set.
             response["Content-Type"] = None
             return response
+
+
 # [END gae_blobstore_handler_django]
 
 
diff --git a/appengine/standard_python3/bundled-services/blobstore/flask/main.py b/appengine/standard_python3/bundled-services/blobstore/flask/main.py
index 019cb5c45b15..ee1b888504c1 100644
--- a/appengine/standard_python3/bundled-services/blobstore/flask/main.py
+++ b/appengine/standard_python3/bundled-services/blobstore/flask/main.py
@@ -59,6 +59,8 @@ def view_photo(photo_key):
 def upload_photo():
     """Upload handler called by blobstore when a blob is uploaded in the test."""
     return PhotoUploadHandler().post()
+
+
 # [END gae_blobstore_handler_flask]
 
 
diff --git a/appengine/standard_python3/bundled-services/deferred/flask/main.py b/appengine/standard_python3/bundled-services/deferred/flask/main.py
index 14be2d8760ab..5ed96bcf21e3 100644
--- a/appengine/standard_python3/bundled-services/deferred/flask/main.py
+++ b/appengine/standard_python3/bundled-services/deferred/flask/main.py
@@ -61,4 +61,6 @@ def custom_deferred():
     print("Executing deferred task.")
     # request.environ contains the WSGI `environ` dictionary (See PEP 0333)
     return deferred.Handler().post(request.environ)
+
+
 # [END gae_deferred_handler_flask]
diff --git a/appengine/standard_python3/bundled-services/mail/django/main.py b/appengine/standard_python3/bundled-services/mail/django/main.py
index 89f7ff27d771..05ba58e2d7e0 100644
--- a/appengine/standard_python3/bundled-services/mail/django/main.py
+++ b/appengine/standard_python3/bundled-services/mail/django/main.py
@@ -58,12 +58,19 @@ def send_mail(address, body):
     if address is None:
         return HttpResponse(content="Error: Missing email address", status=400)
 
-    mail.send_mail(
-        sender=f"demo-app@{project_id}.appspotmail.com",
-        to=address,
-        subject="App Engine Outgoing Email",
-        body=body,
-    )
+    try:
+        mail.send_mail(
+            sender=f"demo-app@{project_id}.appspotmail.com",
+            to=address,
+            subject="App Engine Outgoing Email",
+            body=body,
+        )
+    except Exception as e:
+        print(f"Sending mail to {address} failed with exception {e}.")
+        return HttpResponse(
+            content=f"Exception {e} when sending mail to {address}.",
+            status=500,
+        )
 
     print(f"Successfully sent mail to {address}.")
     return HttpResponse(content=f"Successfully sent mail to {address}.", status=201)
@@ -79,6 +86,8 @@ def receive_mail(request):
         break
 
     return HttpResponse("OK")
+
+
 # [END gae_mail_handler_receive_django]
 
 
@@ -91,6 +100,8 @@ def receive_bounce(request):
     print(f"Bounce notification: {bounce_message.notification}")
 
     return HttpResponse("OK")
+
+
 # [END gae_mail_handler_bounce_django]
 
 
diff --git a/appengine/standard_python3/bundled-services/mail/django/main_test.py b/appengine/standard_python3/bundled-services/mail/django/main_test.py
index d0026eebf7c0..12eb5c211727 100644
--- a/appengine/standard_python3/bundled-services/mail/django/main_test.py
+++ b/appengine/standard_python3/bundled-services/mail/django/main_test.py
@@ -90,7 +90,7 @@ def test_send_receive(version):
     assert "Successfully sent mail" in response.text
 
     # Give the mail some time to be delivered and logs to post
-    time.sleep(30)
+    time.sleep(60)
 
     # Fetch logs to check messages on received mail
     entries = gcloud_cli(
diff --git a/appengine/standard_python3/bundled-services/mail/flask/main.py b/appengine/standard_python3/bundled-services/mail/flask/main.py
index 6b87eb2f1d64..86735bc4540d 100644
--- a/appengine/standard_python3/bundled-services/mail/flask/main.py
+++ b/appengine/standard_python3/bundled-services/mail/flask/main.py
@@ -56,12 +56,16 @@ def send_mail():
         print("Error: missing email address")
         return "Error: Missing email address", 400
 
-    mail.send_mail(
-        sender=f"demo-app@{project_id}.appspotmail.com",
-        to=address,
-        subject="App Engine Outgoing Email",
-        body=request.form.get("body"),
-    )
+    try:
+        mail.send_mail(
+            sender=f"demo-app@{project_id}.appspotmail.com",
+            to=address,
+            subject="App Engine Outgoing Email",
+            body=request.form.get("body"),
+        )
+    except Exception as e:
+        print(f"Sending mail to {address} failed with exception {e}.")
+        return f"Exception {e} when sending mail to {address}.", 500
 
     print(f"Successfully sent mail to {address}.")
     return f"Successfully sent mail to {address}.", 201
@@ -77,6 +81,8 @@ def receive_bounce():
     print("Bounce notification: ", bounce_message.notification)
 
     return "OK", 200
+
+
 # [END gae_mail_handler_bounce_flask]
 
 
@@ -92,4 +98,6 @@ def receive_mail(path):
         break
 
     return "OK", 200
+
+
 # [END gae_mail_handler_receive_flask]
diff --git a/appengine/standard_python3/bundled-services/mail/flask/main_test.py b/appengine/standard_python3/bundled-services/mail/flask/main_test.py
index d0026eebf7c0..12eb5c211727 100644
--- a/appengine/standard_python3/bundled-services/mail/flask/main_test.py
+++ b/appengine/standard_python3/bundled-services/mail/flask/main_test.py
@@ -90,7 +90,7 @@ def test_send_receive(version):
     assert "Successfully sent mail" in response.text
 
     # Give the mail some time to be delivered and logs to post
-    time.sleep(30)
+    time.sleep(60)
 
     # Fetch logs to check messages on received mail
     entries = gcloud_cli(
diff --git a/appengine/standard_python3/bundled-services/mail/wsgi/main.py b/appengine/standard_python3/bundled-services/mail/wsgi/main.py
index 0e6058117ac0..51ccecceda06 100644
--- a/appengine/standard_python3/bundled-services/mail/wsgi/main.py
+++ b/appengine/standard_python3/bundled-services/mail/wsgi/main.py
@@ -36,6 +36,8 @@ def HelloReceiver(environ, start_response):
     response = http.HTTPStatus.OK
     start_response(f"{response.value} {response.phrase}", [])
     return ["success".encode("utf-8")]
+
+
 # [END gae_mail_handler_receive_wsgi]
 
 
@@ -54,6 +56,8 @@ def BounceReceiver(environ, start_response):
     response = http.HTTPStatus.OK
     start_response(f"{response.value} {response.phrase}", [])
     return ["success".encode("utf-8")]
+
+
 # [END gae_mail_handler_bounce_wsgi]
 
 
@@ -90,12 +94,17 @@ def HomePage(environ, start_response):
             print("Error: missing email address")
             return "Error: Missing email address", 400
 
-        mail.send_mail(
-            sender=f"demo-app@{project_id}.appspotmail.com",
-            to=address,
-            subject="App Engine Outgoing Email",
-            body=form.get("body")[0],
-        )
+        try:
+            mail.send_mail(
+                sender=f"demo-app@{project_id}.appspotmail.com",
+                to=address,
+                subject="App Engine Outgoing Email",
+                body=form.get("body")[0],
+            )
+        except Exception as e:
+            print(f"Sending mail to {address} failed with exception {e}.")
+            start_response("500 SERVER ERROR")
+            return [f"Exception {e} when sending mail to {address}.".encode("utf-8")]
 
         print(f"Successfully sent mail to {address}.")
 
diff --git a/appengine/standard_python3/bundled-services/mail/wsgi/main_test.py b/appengine/standard_python3/bundled-services/mail/wsgi/main_test.py
index d0026eebf7c0..12eb5c211727 100644
--- a/appengine/standard_python3/bundled-services/mail/wsgi/main_test.py
+++ b/appengine/standard_python3/bundled-services/mail/wsgi/main_test.py
@@ -90,7 +90,7 @@ def test_send_receive(version):
     assert "Successfully sent mail" in response.text
 
     # Give the mail some time to be delivered and logs to post
-    time.sleep(30)
+    time.sleep(60)
 
     # Fetch logs to check messages on received mail
     entries = gcloud_cli(