好的，首先，这将是一个单用户应用程序。作为开发人员，您将是唯一使用它的人，而您只是以编程方式发送电子邮件，就可以开始澄清一些事情。

1. 您无需验证此应用程序。是的，您只需要像以前一样通过该屏幕。不用担心。not a verified application
2. 通过单击按钮在生产环境中设置应用程序。将使你能够请求不会过期的刷新令牌。你想要这个。同样，请忽略显示您需要验证不需要的应用的屏幕。send to production
3. 测试用户，只要仅使用创建项目的用户登录，就不需要测试用户。忽略它。
4. 它只是您使用应用程序使用范围https://mail.google.com/
5. 不要担心将范围添加到 google cloud 项目，它只是为了验证。重要的是代码中的内容。

好了，一切都清楚了。

您现在有两个选择。

1. XOauth2，这就是你现在正在做的事情。
2. 应用程序密码。只需在您的Google帐户上创建一个应用程序密码，然后使用它来代替您的实际Google密码，您现有的代码就可以了。我如何使用 Python 发送电子邮件。在2.2分钟内平坦！

Xoauth2

如果你想使用 XOauth2，那么你可以使用 Google api python 客户端库来帮助你获取所需的授权令牌

#   To install the Google client library for Python, run the following command:
#   pip install --upgrade google-api-python-client google-auth-httplib2 google-auth-oauthlib


from __future__ import print_function

import base64
import os.path
import smtplib
from email.mime.text import MIMEText

import google.auth.exceptions
from google.auth.transport.requests import Request
from google.oauth2.credentials import Credentials
from google_auth_oauthlib.flow import InstalledAppFlow
from googleapiclient.errors import HttpError

# If modifying these scopes, delete the file token.json.
SCOPES = ['https://mail.google.com/']

# usr token storage

USER_TOKENS = 'token.json'

# application credentials

CREDENTIALS = 'C:\YouTube\dev\credentials.json'


def getToken() -> str:
    """ Gets a valid Google access token with the mail scope permissions. """

    creds = None

    # The file token.json 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(USER_TOKENS):
        try:
            creds = Credentials.from_authorized_user_file(USER_TOKENS, SCOPES)
            creds.refresh(Request())
        except google.auth.exceptions.RefreshError as error:
            # if refresh token fails, reset creds to none.
            creds = None
            print(f'An error occurred: {error}')
    # 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, SCOPES)
            creds = flow.run_local_server(port=0)
        # Save the credentials for the next run
        with open(USER_TOKENS, 'w') as token:
            token.write(creds.to_json())

    try:

        return creds.token
    except HttpError as error:
        # TODO(developer) - Handle errors from authorization request.
        print(f'An error occurred: {error}')


def generate_oauth2_string(username, access_token, as_base64=False) -> str:

    # creating the authorization string needed by the auth server.
    #auth_string = 'user=%s\1auth=Bearer %s\1\1' % (username, access_token)

    auth_string = 'user=' + username + '\1auth=Bearer ' + access_token + '\1\1'
    if as_base64:
        auth_string = base64.b64encode(auth_string.encode('ascii')).decode('ascii')
    return auth_string


def send_email(host, port, subject, msg, sender, recipients):
    access_token = getToken()
    auth_string = generate_oauth2_string(sender, access_token, as_base64=True)

    msg = MIMEText(msg)
    msg['Subject'] = subject
    msg['From'] = sender
    msg['To'] = ', '.join(recipients)

    server = smtplib.SMTP(host, port)
    server.starttls()
    server.docmd('AUTH', 'XOAUTH2 ' + auth_string)
    server.sendmail(sender, recipients, msg.as_string())
    server.quit()


def main():
    host = "smtp.gmail.com"
    port = 587

    user = "[email protected]"

    subject = "Test email Oauth2"
    msg = "Hello world"
    sender = user
    recipients = [user]
    send_email(host, port, subject, msg, sender, recipients)


if __name__ == '__main__':
    main()