How to use Mailjet from Google App Engine

Question

I'm integrating Mailjet into my Google App Engine application. I'm at the point where I can successfully send email from the local development server. But when I deploy my application and try to send an email, the Mailjet client library apparently hits an error when trying to connect to the Mailjet rest API.

Caused by NewConnectionError(': Failed to establish a new connection: [Errno -3] Temporary failure in name resolution'

I basically followed instructions from
https://cloud.google.com/appengine/docs/standard/python/mail/sending-messages
and
https://cloud.google.com/appengine/docs/standard/python/tools/using-libraries-python-27

Code I added to integrate mailjet.
requirements.txt:

certifi==2019.6.16
chardet==3.0.4
idna==2.8
mailjet-rest==1.3.3
requests==2.22.0
urllib3==1.25.3

app.yaml:

...
libraries:
- name: ssl
  version: latest

main.py:

from mailjet_rest import Client
...
#calling this function to send email
def mailjet_sendmail(to_address, subject, body):
    api_key = '***'
    api_secret = '***'
    mailjet = Client(auth=(api_key, api_secret), version='v3.1')
    data = {
      'Messages': [
        {
          "From": {
            "Email": "noreply@mydomain.com",
            "Name": "mydomain.com"
          },
          "To": [
            {
              "Email": to_address,
            }
          ],
          "Subject": subject,
          "TextPart": body,
        }
      ]
    }
    result = mailjet.send.create(data=data)

When I call mailjet.send.create, the following exception shows in the error logs:

ApiError: HTTPSConnectionPool(host='api.eu.mailjet.com', port=443): Max retries exceeded with url: /v3.1/send (Caused by NewConnectionError('<urllib3.connection.VerifiedHTTPSConnection object at 0x2a66ef5e1950>: Failed to establish a new connection: [Errno -3] Temporary failure in name resolution',))

        at api_call (/base/data/home/apps/s~***/20190828t114640.420634513089712020/mailjet_rest/client.py:110)
        at create (/base/data/home/apps/s~***/20190828t114640.420634513089712020/mailjet_rest/client.py:62)
        at mailjet_sendmail (/base/data/home/apps/s~***/20190828t114640.420634513089712020/main.py:80)
        at post (/base/data/home/apps/s~***/20190828t114640.420634513089712020/main.py:379)
        ...

It looks as if it fails to resolve api.eu.mailjet.com.

Is there anything I need to do to enable DNS lookup in Google App Engine? Can someone show a fully working example?

Note that exactly the same code works on my PC running the local development server.

Thanks

Fred

Answer 1

After searching further, I actually found the answer to my own question.

The only problem was that no billing account was linked to the project. For the rest everything was done correctly.

Hope this helps others.

Fred