Build a Ghost Messenger API with Node.js for Delayed Emails

Have you ever wanted to schedule emails to send themselves days, weeks, or even months later? Whether it’s for birthday reminders, timed marketing campaigns, or automated follow-ups, a “Ghost Messenger” API can handle it. In this guide, you’ll learn to build a secure, scalable Node.js Express.js API that queues and sends emails in the future—perfect for developers.

Why Build a Ghost Messenger API?

• Automate time-sensitive communications without manual intervention
• Improve user engagement with perfectly timed emails
• Solve real-world problems like event reminders or subscription renewals
• Ideal for startups, SaaS products, or personal projects

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Prerequisites

1. Basic knowledge of JavaScript and Node.js
2. Node.js v18+ installed
3. MongoDB (or any database for storing scheduled jobs)
4. SMTP credentials (Gmail, SendGrid, or Mailgun)

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Step 1: Set Up the Project

mkdir ghost-messenger && cd ghost-messenger
npm init -y
npm install express mongoose node-cron nodemailer dotenv

Step 2: Build the Core API Structure

Create app.js:

const express = require('express');
const mongoose = require('mongoose');
const cron = require('node-cron');
const nodemailer = require('nodemailer');
require('dotenv').config();

const app = express();
app.use(express.json());

// Connect to MongoDB
mongoose.connect(process.env.MONGODB_URI)
  .then(() => console.log('Connected to MongoDB'))
  .catch(err => console.error('Connection failed:', err));

// Define Email Schema
const emailSchema = new mongoose.Schema({
  recipient: String,
  subject: String,
  body: String,
  sendAt: Date,
  status: { type: String, default: 'scheduled' }
});

const EmailJob = mongoose.model('EmailJob', emailSchema);

Step 3: Create the Email Service

Add SMTP configuration in .env:

SMTP_HOST=smtp.example.com
SMTP_PORT=587
SMTP_USER=your_email@domain.com
SMTP_PASS=your_password

Implement the email sender:

const transporter = nodemailer.createTransport({
  host: process.env.SMTP_HOST,
  port: process.env.SMTP_PORT,
  auth: {
    user: process.env.SMTP_USER,
    pass: process.env.SMTP_PASS
  }
});

// Cron job to check every minute
cron.schedule('* * * * *', async () => {
  const jobs = await EmailJob.find({
    sendAt: { $lte: new Date() },
    status: 'scheduled'
  });

  jobs.forEach(async (job) => {
    await transporter.sendMail({
      from: '"Ghost Messenger" <noreply@ghostmessenger.com>',
      to: job.recipient,
      subject: job.subject,
      text: job.body
    });
    
    job.status = 'sent';
    await job.save();
  });
});

Step 4: Create API Endpoints

app.post('/schedule-email', async (req, res) => {
  try {
    const { recipient, subject, body, sendAt } = req.body;
    const newJob = new EmailJob({ recipient, subject, body, sendAt });
    await newJob.save();
    res.status(201).json({ message: 'Email scheduled successfully', id: newJob._id });
  } catch (error) {
    res.status(500).json({ error: 'Scheduling failed' });
  }
});

app.get('/jobs/:id', async (req, res) => {
  try {
    const job = await EmailJob.findById(req.params.id);
    res.json(job);
  } catch (error) {
    res.status(404).json({ error: 'Job not found' });
  }
});

Step 5: Test and Deploy

1. Test locally with Postman:

POST http://localhost:3000/schedule-email
{
  "recipient": "user@example.com",
  "subject": "Your Future Message",
  "body": "This email was sent from the past!",
  "sendAt": "2024-12-31T23:59:00"
}

2. Deploy to Heroku/DigitalOcean with:

git push heroku main

Best Practices for Production

1. Security: Use JWT authentication for API endpoints
2. Error Handling: Implement retries for failed emails
3. Logging: Track sent emails and failures
4. Scalability: Use Redis BullMQ for job queues in high-traffic apps

FAQs

Q: Can I use this with free email providers like Gmail?
A: Yes, but enable “Less Secure Apps” in Gmail settings or use OAuth2.

Q: How far in advance can I schedule emails?
A: Years! The cron job checks every minute for due emails.

Q: Will this work after server restart?
A: Yes—jobs are stored in MongoDB and processed automatically.

Ready to automate your future communications? Deploy your Ghost Messenger API today and never miss perfect timing again! 👻📨