Javascript 防止Node.js应用程序导致错误\u太多\u重定向

我的网站出现问题。我相信主要是Node.js应用程序和我的联系人页面。我测试了一些东西，多次点击提交按钮，导致了ERR\u too\u many\u重定向错误

我的根域mydomainname.com连接到Firebase，而我的Node.js应用程序api.mydomainname.com连接到Heroku

我理解该错误是由于我的域被定向到另一个域以向自己发送电子邮件，并在失败时重定向回我的域而导致的。我不知道如何防止这个错误，也不知道我的网站应该指向哪里

相关代码 index.js

const express = require('express'); //Needed to launch server.
const bodyParser = require('body-parser');
const cors = require('cors'); //Needed to disable sendgrid security.
const sendGrid = require('@sendgrid/mail'); //Access SendGrid library to send emails.
sendGrid.setApiKey(process.env.SENDGRID_API_KEY);
const app = express(); //Alias from the express function.

app.use(bodyParser.json());

app.use(cors());

app.use((req, res, next) => {
    res.setHeader('Access-Control-Allow-Origin', '*'); // Change later to only allow our server
    res.setHeader('Access-Control-Allow-Methods', 'GET, POST, PUT, PATCH, DELETE');
    res.setHeader('Access-Control-Allow-Headers', 'Content-Type, Authorization');
    next();
});

app.get('/api', (req, res, next) => {
    res.send('API Status: Running');
});

app.post('/api/email', (req, res, next) => {
    console.log(req.body);
    const msg = {
        to: 'my@email.com',
        from: req.body.email,
        subject: req.body.subject,
        text: req.body.message
    }
    sendGrid.send(msg)
        .then(result => {
            res.status(200).json({
                success: true
            });
        })
        .catch(err => {
            console.log('error: ', err);
            res.status(401).json({
                success: false
            });
        });
});

app.listen(process.env.PORT || 4000);