mail-delivery-service/index.js

const express = require('express')
const app = express()
app.use(express.json())
const port = 3103

var nodemailer = require("nodemailer");
var chalk = require("chalk");

check_env_variables();

app.get('/', (req, res) => {
   res.send("Mail Delivery Service");
})

app.post('/send', (req, res) => {
    console.log(req.body);
    res.status(200).end();
    send_mail(req.body);
})

app.listen(port, () => {
  console.log(`Mail Delivery Service listening at ${chalk.cyan(`http://localhost:${port}`)}`);
})

var send_mail = function(msg_data) {
    var mail_msg = {
        to: msg_data.to,
        from: msg_data.from,
        subject: msg_data.subject,
        html: msg_data.message,
    }
    // create Nodemailer SES transporter
    var transporter = nodemailer.createTransport({
        host: process.env.AWS_SES_URL,
        port: 587,
        secure: false, // upgrade later with STARTTLS
        auth: {
          user: process.env.AWS_SES_SMTP_USERNAME,
          pass: process.env.AWS_SES_SMTP_PASSWORD
        }
    });
    transporter.sendMail(mail_msg, function (err, info) {
        if (err) {
            console.log("Error sending email");
            console.log(err);
        } else {
            console.log("Email sent successfully");
            console.log(info);
        }
    });
}

// Some checking to see if environment variables are set on statup and show errors if not
var check_env_variables = function() {
    var env = process.env;
    var e = `${chalk.red(`ERROR:`)}`;
    if(env.AWS_SES_URL != "" && env.AWS_SES_URL != undefined){
        console.log(`Delivery server URL: ${chalk.green(`\'${env.AWS_SES_URL}\'`)}`);
    } else {
        var v = `${chalk.yellow(`\'AWS_SES_URL\'`)}`;
        console.log(`${e} AWS SES URL is missing. To fix this, add ${v} to the environment variables.`);
    }
    var has_username = env.AWS_SES_SMTP_USERNAME != "" && env.AWS_SES_SMTP_USERNAME != undefined;
    var has_password = env.AWS_SES_SMTP_PASSWORD != "" && env.AWS_SES_SMTP_PASSWORD != undefined;
    if(has_username && has_password){
        console.log(`AWS SES authentication is set with username: ${chalk.italic(env.AWS_SES_SMTP_USERNAME)}`);
    } else {
        if(!has_username){
            var v = `${chalk.yellow(`\'AWS_SES_SMTP_USERNAME\'`)}`;
            console.log(`${e} AWS SES needs a username. Add ${v} to the environment variables.`);
        }
        if(!has_password){
            var v = `${chalk.yellow(`\'AWS_SES_SMTP_PASSWORD\'`)}`;
            console.log(`${e} AWS SES needs a password. Add ${v} to the environment variables.`);
        }
    }
}