Automate email responses with GPT-4o-mini and human review in Gmail

This n8n template demonstrates a “Human-in-the-Loop” workflow where AI automatically drafts replies to inbound emails, which are then reviewed and approved by a human before being sent. This powerful pattern ensures both the efficiency of AI and the quality assurance of human oversight.

Use cases are many: Streamline sales inquiry responses, manage first-level customer support, handle initial recruitment communications, or any business process that requires personalized yet consistent email replies.

Good to know

- At the time of writing, the cost per execution depends on your OpenAI API usage. This workflow uses a cost-effective model like gpt-4o-mini. See [OpenAI Pricing](https://openai.com/pricing) for updated info. - The AI’s knowledge base and persona are fully customizable within the Basic LLM Chain node’s prompt.

How it works

1. The Gmail Trigger node starts the workflow whenever a new email arrives in the specified inbox. 2. The Classify Potential Leads node uses AI to determine if the incoming email is a potential lead. If not, the workflow stops. 3. The Basic LLM Chain, powered by an OpenAI Chat Model, generates a draft reply based on a detailed system prompt and your internal knowledge base. 4. A Structured Output Parser is crucially used to force the AI’s output into a reliable JSON format ({"subject": "...", "body": "..."}), preventing errors in subsequent steps. 5. The Send for Review Gmail node sends the AI-generated draft to a human reviewer and pauses the workflow, waiting for a reply. 6. The IF node checks the reviewer’s reply for approval keywords (e.g., “approve”, “承認”). 7. If approved, the ✅ Send to Customer Gmail node sends the final email to the original customer. 8. If not approved, the reviewer’s feedback is treated as a revision request, and the workflow loops back to the Basic LLM Chain to generate a new draft incorporating the feedback.

How to use

- Gmail Trigger node: Configure with your own Gmail account credentials. - Send for Review node: Replace the placeholder email reviewer@example.com with the actual reviewer's email address. - IF node: You can customize the approval keywords to match your team’s vocabulary. - OpenAI Nodes: Ensure your OpenAI credentials are set up. You can select a different model if needed, but the prompt is optimized for models like GPT-4o mini.