🏠 Mailo: AI Email Replies, Seamlessly Delivered

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

What I Built

I built Mailo, an email-based AI assistant powered by Postmark and OpenAI’s GPT-4. You simply send an email to the designated mail address, and Mailo replies with a thoughtful, relevant, and human-like response within seconds. It feels like you're emailing a helpful friend who’s really good at everything. Whether you're asking a technical question, seeking advice, or just curious about something—Mailo reads your message, understands the context, and sends a high-quality AI-generated reply.

The magic is in the simplicity: you don’t need to sign up, install anything, or learn a new interface. Just send an email like you normally would. You can also reply to Mailo’s responses to continue the conversation—threaded replies are fully supported. It’s as natural and frictionless as having an ongoing chat, but over email. The goal was to make AI feel invisible and effortlessly integrated into a tool everyone already uses daily: email.

Demo

mailo-nine.vercel.app

The landing page:

Sending an email to Mailo:

Receiving an email from Mailo:

Code Repository

shravzzv / mailo

Mailo is an AI-powered email assistant that lets you ask questions and get intelligent replies — all through email. No app, no login, just email magic.

📬 Mailo

Mailo is a lightweight AI-powered email assistant that works entirely over email. No apps. No logins. Just send an email and get smart, context-aware replies delivered straight to your inbox — powered by GPT.

Built for the dev.to Postmark Challenge: Inbox Innovators.

✨ Features

• 📩 Email-first Interface — Just send an email to interact, no account needed.
• 🧠 GPT-Powered Intelligence — Smart, human-like responses tailored to your message.
• ⚡ Fast & Lightweight — No bloated UI, just good old email.
• 🛡️ Privacy-first — Only the message content is used to generate replies.

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🛠️ Tech Stack

Tech	Role
Next.js 15	API routes + landing page
Postmark	Inbound email parsing
Nodemailer	Sending reply emails
OpenAI (via GitHub Models)	LLM backend
TypeScript	Type safety

📦 Architecture

User → (sends email) to Postmark → Next.js Webhook → GPT-4.1 (GitHub) → Mailo Nodemailer → replies

🧪 Testing the App

1. Click the Try…

View on GitHub

How I Built It

🔧 Tech Stack

Mailo is built on top of modern, minimal technologies designed for speed, privacy, and simplicity:

• Frontend: Next.js (App Router) + Tailwind CSS for styling and responsive UI.
• Backend: Next.js API routes for handling outbound mail, webhook payloads, and AI response generation.
• AI Engine: OpenAI’s GPT-4 for smart, high-quality email replies.
• Email Infrastructure:
  • Postmark's inbound stream for receiving emails.
  • Custom MX record setup to route all emails sent to [e-mail] directly into a Postmark Inbound Stream, which then hits a webhook in my app.

🧪 Testing instructions:

Testing Mailo is easy. All you need is an email account:

1. Go to mailo-nine.vercel.app and click Try it now, or just send an email directly to [e-mail].
2. Use a clear subject line as your question.
3. Optionally, add extra context or details in the body of the email.
4. Wait a few seconds — Mailo will respond to you automatically.
5. Got follow-up questions? Just reply to the email you received — Mailo understands and continues the conversation intelligently.

⚠️ Note: If you don’t see a reply, check your spam folder. All replies are sent within a few seconds.

♿ Accessibility

I made a conscious effort to ensure Mailo is as accessible as possible:

• ✅ Semantic HTML and ARIA-aware elements
• ✅ Keyboard navigability across all interactive components
• ✅ Responsive and legible on mobile, tablet, and desktop
• ✅ Email-first design — users who don't visit the website still get the full Mailo experience

✨ Highlights & Learnings

• I learned to configure custom MX records and route emails directly through Postmark's infrastructure — giving me complete control over inbound email flows.
• I built a robust, privacy-first workflow that requires zero user data storage.
• I realized the power of using email as an API — the interface is already everywhere, no onboarding needed. -It was incredibly fun (and challenging) to make email feel conversational and alive with AI.

Thanks for checking out Mailo — I'm excited to see where this goes next! 👋 If you have feedback, questions, or ideas, feel free to… well, just send me an email. Built for the Postmark Inbox Innovators Hackathon with love.💛

Comments

[Niko from Axrisi]

I was interested how you did threads using postmark, but then realised you use postmark only for inbound emails? and then using titan.email and nodemailer for sending emails to user?

[Sai Shravan Vadla]

Yes. It isn't exactly threads but you can ask followup questions within a single chat on mail.

[Nathan Tarbert]

pretty cool tbh, i use email a ton so this just makes sense - you think the secret to real adoption is cutting friction or is there more to it?

[Sai Shravan Vadla]

Thank you. It means a lot to me that you think my project is cool. I haven't really thought about adoption that much, I just wanted to build something cool for the hackathon. Cheers.