How to send an email through gmail without enabling 'insecure access'?

Question

Google are pushing us to improve the security of script access to their gmail smtp servers. I have no problem with that. In fact I\'m happy to help.

But they\'re n

Answer 1

Updated sample for Python 3, and GMail's current API, below.

Note that to get the credentials.json file below, you'll need to create an Oauth client ID credential here, after selecting the relevant GCP project. Once you've created it you'll be shown the client key and client secret. Close that prompt, and click the down arrow next to the account. This is the file you'll need.

import base64
import logging
import mimetypes
import os
import os.path
import pickle
from email.mime.text import MIMEText
from google_auth_oauthlib.flow import InstalledAppFlow
from google.auth.transport.requests import Request
from googleapiclient import errors
from googleapiclient.discovery import build

def get_service():
    """Gets an authorized Gmail API service instance.

    Returns:
        An authorized Gmail API service instance..
    """    

    # If modifying these scopes, delete the file token.pickle.
    SCOPES = [
        'https://www.googleapis.com/auth/gmail.readonly',
        'https://www.googleapis.com/auth/gmail.send',
    ]

    creds = None
    # The file token.pickle stores the user's access and refresh tokens, and is
    # created automatically when the authorization flow completes for the first
    # time.
    if os.path.exists('token.pickle'):
        with open('token.pickle', 'rb') as token:
            creds = pickle.load(token)
    # If there are no (valid) credentials available, let the user log in.
    if not creds or not creds.valid:
        if creds and creds.expired and creds.refresh_token:
            creds.refresh(Request())
        else:
            flow = InstalledAppFlow.from_client_secrets_file(
                'credentials.json', SCOPES)
            creds = flow.run_local_server(port=0)
        # Save the credentials for the next run
        with open('token.pickle', 'wb') as token:
            pickle.dump(creds, token)

    service = build('gmail', 'v1', credentials=creds)
    return service

def send_message(service, sender, message):
  """Send an email message.

  Args:
    service: Authorized Gmail API service instance.
    user_id: User's email address. The special value "me"
    can be used to indicate the authenticated user.
    message: Message to be sent.

  Returns:
    Sent Message.
  """
  try:
    sent_message = (service.users().messages().send(userId=sender, body=message)
               .execute())
    logging.info('Message Id: %s', sent_message['id'])
    return sent_message
  except errors.HttpError as error:
    logging.error('An HTTP error occurred: %s', error)

def create_message(sender, to, subject, message_text):
  """Create a message for an email.

  Args:
    sender: Email address of the sender.
    to: Email address of the receiver.
    subject: The subject of the email message.
    message_text: The text of the email message.

  Returns:
    An object containing a base64url encoded email object.
  """
  message = MIMEText(message_text)
  message['to'] = to
  message['from'] = sender
  message['subject'] = subject
  s = message.as_string()
  b = base64.urlsafe_b64encode(s.encode('utf-8'))
  return {'raw': b.decode('utf-8')}

if __name__ == '__main__':
    logging.basicConfig(
        format="[%(levelname)s] %(message)s",
        level=logging.INFO
    )

    try:
        service = get_service()
        message = create_message("from@gmail.com", "to@gmail.com", "Test subject", "Test body")
        send_message(service, "from@gmail.com", message)

    except Exception as e:
        logging.error(e)
        raise