💌 Build Your Own AI Email Manager with n8n, OpenAI & Slack

(Simple Guide to Automating Emails, Writing Replies & Sending Slack Alerts)

---

✨ Introduction

Are you tired of sorting, replying, and checking every single email manually? Imagine if an AI agent could handle all your emails — label them, write responses, and even send alerts to your Slack — while you relax or focus on real work.

In this guide, you’ll learn how to build such an AI-powered system using:

• n8n (Open-source automation tool)
• OpenAI (to generate responses)

And the best part? You don’t need to write a single line of code!

---

🛠️ Tools You'll Use

1. n8n – To build the no-code automation flow
2. OpenAI (Chat Model) – To classify emails & generate replies
3. Gmail – As the mail platform

---

🚀 Step-by-Step Guide

---

1. Setup n8n (Cloud or Self-Hosted)

• You can run n8n via their official cloud or install it self-hosted (cheaper option).
• The creator hosted it for \$7/month on railway.app instead of \$20 on n8n Cloud.

👉 Once inside n8n Dashboard, create a New Workflow.

---

2. Add the Gmail Trigger

• Add a Gmail node and choose "On Message Received."
• If this is your first time, you’ll need to set up Gmail credentials (n8n docs can guide you).
• Set polling time to “Every Minute” to check your inbox for new emails.
• Test this node — you’ll see n8n can now detect new emails.

---

3. Classify Email Content using OpenAI

• Add the Text Classifier node.

• Set it to use the email body (snippet) from Gmail.

• Define your own email categories/labels. Example:

  • Consultation Request
  • Billing
  • Customer Support

• You can also add a simple System Prompt (for LLM guidance).

• Set up OpenAI API credentials in n8n (you can use OpenAI's API key platform).

• Use gpt-4o-mini model (or better, use GPT-4o in production).

👉 Test this node — your email should now get classified into one of your 3 labels.

---

4. Apply Labels to Gmail Emails

• After classifying the email, add a Gmail node to “Add Label to Message.”

• Pass the Email ID from the earlier node.

• Select the correct label depending on the classification:

  • Consultation Request
  • Billing
  • Customer Support

• You can duplicate this step for each label and connect the correct paths.

👉 Test this node — emails will be labeled in Gmail properly.

---

5. Auto-Draft Replies for “Consultation Requests”

• If the email is classified as Consultation, let AI write a draft reply.

• Add an OpenAI Chat Model node:

  • Use the same API key & model (gpt-4o-mini or gpt-4o).
  • Prompt it to write a reply based on the email body.

• Next, add a Gmail node to “Create Draft”:

  • Pull the AI-generated reply.
  • Add Thread ID and Subject to make sure the reply matches the right email.

👉 Test this node — a draft reply should appear in your Gmail drafts!

--