Inbox Translator: Automatic Email Translation Made Easy

This is a submission for the Postmark Challenge: Inbox Innovators.

What I Built

Inbox Translator is an AI-powered email translation app that automatically translates incoming emails into English using OpenRouter’s GPT-3.5-turbo model. Integrated with Postmark’s inbound email parsing, the app listens for emails sent to a dedicated address, translates their content seamlessly, and sends back the translated message to the sender.

Designed with a sleek, dark-themed, responsive UI, Inbox Translator offers users a simple way to overcome language barriers in email communication without any manual effort. This solution is ideal for professionals, businesses, and anyone who regularly receives emails in different languages and wants fast, reliable translations directly in their inbox.

Demo

Demo link

Code Repository

Repo Link

How I Built It

🛠 Step-by-Step Guide: Building the Inbox Translator App

1️⃣ Project Setup
Tools: Node.js, Express, EJS, TailwindCSS

Initialized the project using npm init

Installed required packages:
npm install express ejs body-parser dotenv postmark node-fetch

Set up project folders:
/views → EJS templates
/public → Static CSS (Tailwind)
index.js → Main server logic
.env → Environment config


2️⃣ Set Up Postmark for Inbound Emails
Steps:
Created a Postmark account and set up a new Inbound Stream.
Set your Inbound Webhook URL to your deployed endpoint:
(https://inbox-translator.onrender.com/inbound-email)

Verified the domain or used Postmark’s testing domain (inbound.postmarkapp.com)

3️⃣ Handling Incoming Emails
How it works:
The webhook /inbound-email receives incoming email data from Postmark.
It logs the sender and the original message content.

4️⃣ Language Detection & Conditional Translation
Tools: LibreTranslate + OpenRouter GPT-3.5

Used LibreTranslate to detect if the email is already in English.

If not, used OpenRouter (GPT-3.5-turbo) to translate the message to English.

Example logic:if (language !== 'en') {
// translate using OpenRouter AI
}

5️⃣ Sending Back the Translated Email
Used Postmark’s sendEmail method to reply to the original sender.

Dynamic subject and body:Subject: "Translated Email (Inbox Translator)"
TextBody:Here is your translated message:\n\n${translatedText}


6️⃣** Frontend UI — Viewing Translations**
Tools: EJS + Tailwind CSS

Created a dark-themed interface to display email history.

Emails are stored in-memory and rendered as responsive cards.

Added a dark/light toggle and smooth animations.

✅ Summary: Tech Stack

Layer	Tool/Service
Backend	Node.js + Express
Frontend	EJS + Tailwind CSS
Email Engine	Postmark (Inbound + Outbound)
Translation	GPT-3.5-turbo via OpenRouter
Deployment	Render.com

Comments

[Dotallio]

Super practical idea, especially for those of us handling international email. Are you thinking about adding support for translating into other languages too?

[Eunice]

Thank you! I’m really glad you find it practical — that was exactly the goal.

Yes, adding multi-language support is definitely on the roadmap! Right now, it defaults to translating into English to keep the experience simple. But I’m exploring an update where users can set their preferred language, either by configuring it via a UI or detecting it from their email content.

It’d be awesome to let users reply with something like “Translate to French,” and the app would remember that preference going forward. Stay tuned — would love your feedback on which languages you’d want first!