通过服务帐户

Question

我想要实现的是通过nodemailer从我的Web应用程序通过服务帐户向收件人发送邮件。

我从以下链接中获取了参考资料

1. https://developers.google.com/identity/protocols/OAuth2ServiceAccount
2. https://gypsyshen.com/2018/03/01/secure-gmail-access-with-oauth2-and-2lo-in-express/
3. https://nodemailer.com/smtp/oauth2/

以下是代码：

var express = require('express');
var router = express.Router();
var nodemailer = require('nodemailer');
var {google} = require('googleapis');
var serviceKey = require('../key/serviceKey.json');

router.post('/', function(req, res, next){
  var jwtClient = new google.auth.JWT(serviceKey.client_email, null, serviceKey.private_key, ['https://mail.google.com'], null);

  jwtClient.authorize(function(error, token){
    if(error){
      console.log('Error: ' + error);
      res.json({success: false, error: error});
      return;
    }

    console.log('JWT Authorisation Success');

    var transporter = nodemailer.createTransport({
      host : 'smtp.gmail.com',
      port : 465,
      secure : true,
      auth : {
        type : 'OAuth2',
        user : serviceKey.client_email,
        serviceClient : serviceKey.client_id,
        privateKey : serviceKey.private_key,
        accessToken : token.access_token,
        expires : token.expiry_date
      }
    });

    var requestBody = req.body;
    var data = requestBody['data'];    

    var msg = "Data: "+data;

    transporter.sendMail({
      from: serviceKey.client_email,
      to: recipient@abc.com,
      subject : 'Test Mail',
      text : msg
    }, function(error, info){
        if(error){
          console.log("Error: "+error);
        } else {
          console.log("Success: "+info);
        }
    });


  });
});

module.exports = router;

现在我遇到的问题是 - 虽然Console记录了消息“JWT授权成功”，但是当它实际发送邮件时，我收到此错误

  

错误：登录无效：535-5.7.8不接受用户名和密码。   在535 5.7.8了解更多信息   https://support.google.com/mail/?p=BadCredentials v5-v6sm24994162pfd.1    - gsmtp

我无法找到解决方法。请帮忙，并建议一些很好的资源来了解它。

其他信息：服务帐户的角色设置为“服务帐户用户”