Receive SendGrid inbound email parse webhook

Posted on Edited on In

完成了發信功能後, 偶爾還是會有客戶會想透過 Email 聯繫, 所以還是要有個客服信箱來收信, SendGrid 也可以代為收信, 但他不像傳統 mailserver 信件會儲存起來等你上線去收, 而是提供 parse webhook 來讓你自己接收信件內容.

Setting up an MX Record

首先你要在 DNS 上設定 MX Record 如下
https://i.imgur.com/Y2Onu4p.png

設定完如下 (If there is no field for priority, type 10 before the address. e.g. 10 mx.sendgrid.net.)
https://i.imgur.com/FbvPd6q.jpg

使用 Cloud function 接收 webhook

使用 cloud Function 的檔案如下

package.json

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{
  "name": "sample-http",
  "version": "0.0.1",
  "dependencies": {
    "@google-cloud/storage": "^5.0.0",
    "busboy": "^0.3.0",
    "escape-html": "^1.0.3"
  }
}

index.js

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const Busboy = require('busboy');

/**
 * Responds to any HTTP request.
 *
 * @param {!express:Request} req HTTP request context.
 * @param {!express:Response} res HTTP response context.
 */
exports.receiveParsingEmail = (req, res) => {
    var http = require("https");
    console.log("Cloud Function Start : " + req.body.toString());

    let apikey = process.env.apikey;
    let fromaddr = process.env.fromaddr;
    let fromname = process.env.fromname;
    let toaddr = process.env.toaddr;
    let toname = process.env.toname;
    // let mailcontent = req.body.toString();

    console.log("Mail to addr=" + req.body.toString());

    var options = {
        "method": "POST",
        "hostname": "api.sendgrid.com",
        "port": null,
        "path": "/v3/mail/send",
        "headers": {
            "authorization": "Bearer " + apikey,
            "content-type": "application/json"
        }
    };

    var mailreq = http.request(options, function (mailres) {
        var chunks = [];
        mailres.on("data", function (chunk) {
            chunks.push(chunk);
        });
        mailres.on("end", function () {
            var body = Buffer.concat(chunks);
            console.log(body.toString());
        });
    });

    const busboy = new Busboy({ headers: req.headers });
    const fields = {};
    // This code will process each non-file field in the form.
    busboy.on('field', (fieldname, val) => {
        console.log(`Processed field ${fieldname}: ${val}.`);
        fields[fieldname] = val;
    });

    busboy.on('finish', async () => {
        let mailcontent = 'subject:' + '\r\n' + fields.subject + '\r\n';
        mailcontent = mailcontent + '\r\n' + 'from:' + fields.from + '\r\n';
        mailcontent = mailcontent + '\r\n' + 'content:' + fields.text;

        mailreq.write(JSON.stringify({
            personalizations: [{
                to: [{
                    email: toaddr,
                    name: toname
                }],
                subject: "mail notify"
            }],
            content: [{
                type: "text/plain",
                value: mailcontent
            }],
            from: {
                email: fromaddr,
                name: fromname
            }
        }));
        mailreq.end();

        res.status(200).send("OK");
    });
    busboy.end(req.rawBody);
};

以上範例 就可以完成 接收 webhook 再將內容轉發到我們指定的信箱

References

Getting started with the SendGrid API
Setting Up The Inbound Parse Webhook
Cloud Functions HTTP parse multipart/form-data

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