n8n: Summarize Customer Emails with OpenAI

Updated October 17, 2026. Built against the tool’s current screens and checked step by step. How we check this lesson

Your first AI step in n8n doesn't need an agent. In this free lesson a made-up bookkeeping firm pins three customer emails, sends each one to OpenAI's Message a model with a single prompt and the email body dragged in, and gets back a one-sentence summary and the next step. Then an Edit Fields node pulls the answer out of the nested output and adds the sender from the trigger. The summaries in the practice are real answers from GPT-4.1-MINI.

Start here first: n8n: What Is n8n? Build Your First Workflow (module 1 of n8n Automation Toolkit)

In the course: Part 9 · n8n Automation Toolkit (Module 75 of the full course)

Part of: n8n for Beginners: Your First Automations (step 9 of 9)

The real answers

From a test run in n8n Cloud on October 17, 2026, with the prompt "Summarize this customer email in one sentence, then say what we need to do next."

Add the OpenAI node

Search OpenAI (it carries a Free credits tag for new n8n Cloud accounts) and choose Message a model under TEXT ACTIONS. Pick a credential: free credits if you have them, or Create new credential and paste your own API key from platform.openai.com.

Model and prompt

Search the Model list for mini and choose a small model such as GPT-4.1-MINI. Under Message 1 (Role User), paste the instruction into Prompt and drag the email body from INPUT to the end. The node runs once per item: three emails, three answers.

Tidy the answer

The answer sits in output > content > text. Add Edit Fields, expand the earlier trigger in INPUT to drag from, then drag text onto the drop area and rename it summary. Each item now has two plain fields, ready for Slack, a sheet or an email.

Links

• n8n (affiliate link): the workflow tool this lesson teaches (free trial, no credit card).
• OpenAI API keys: where you create your own key.
• n8n docs: OpenAI node: every OpenAI action in n8n.

Disclosure: links marked "affiliate link" are partner links. If you sign up through one, Stepthrough may earn a commission at no extra cost to you. The lesson is free either way and does not depend on it.

Step by step: n8n: Summarize Customer Emails with OpenAI

All 31 steps of the interactive module, in order. In the module you watch each one, then do it yourself in a practice copy that checks your work.

1. Load three emails

1. Add the first step. Clearview Bookkeeping's shared inbox gets dozens of client emails a day, and someone reads each one twice to work out what to do. You'll have AI write a one-line summary and the next step. Click Add first step....

   Clearview Bookkeeping's shared inbox gets dozens of client emails a day. Someone reads each one, twice, to work out what to do. You'll have AI write a short summary, and the next step.

2. Trigger manually. Click Trigger manually. You will use test emails, not a real inbox.

   You'll use test emails, not a real inbox.

3. Open the trigger. Open the trigger.
4. Set mock data. Click set mock data.
5. Paste three emails. Replace the example with three customer emails, each with from, subject and body.

   Replace the example with three customer emails. Each has a from, a subject and a body.

   [{"from":"jordan@lakeside-dental.example","subject":"Invoice question","body":"Hi, we got invoice INV-1042 for $480 but we think we already paid it on October 2 by bank transfer. Can you check and let us know? We don't want to pay twice. Thanks, Jordan"},{"from":"maria@northpoint.example","subject":"Need to move our call","body":"Hello, something came up and I can't make our Thursday 2pm call about the quarterly review. Could we do Friday morning instead, any time before 11? Sorry for the short notice. Maria"},{"from":"sam@brightline.example","subject":"New client referral","body":"Hey! My friend runs a small architecture firm, about 12 people, and is unhappy with her current bookkeeper. She wants monthly bookkeeping and payroll. Okay if I give her your email? Sam"}]

6. Save. Click Save. The OUTPUT shows 3 items.

   Three items.

7. Close the node. Close the node.

2. Ask OpenAI

8. Add a step. Click the + after the trigger.
9. Search for OpenAI. Type OpenAI.
10. OpenAI. Click OpenAI: *Message an assistant or GPT, analyze images, generate audio, etc.* The Free credits tag means new n8n Cloud accounts get some free use.

    See the free credits tag. New n8n Cloud accounts get some free use, so you may not need a key to try it.

11. Message a model. Under TEXT ACTIONS, click Message a model.

    Under text actions, click Message a model. That means, send the AI a prompt, and get an answer back.

12. Open Credential. n8n needs to know whose OpenAI account to use. Click the Credential box.

    n8n needs to know whose OpenAI account to use.

13. Create new credential. Click Create new credential. (On a new n8n Cloud account you may also see free credits here; you can pick those and skip the key.)

    On a new n8n Cloud account, you might see free credits in this list too. If so, you can pick those, and skip the key.

14. Paste your API key. Paste your own OpenAI API key into API Key (from platform.openai.com, API keys). n8n stores it encrypted. Never paste a key into a prompt or a field anywhere else.

    n8n stores it encrypted. Never paste a key anywhere else, like a prompt.

15. Save the credential. Click Save, then close the window.
16. Pick a model. Resource is Text and Operation is Message a Model. Open Model.

    Resource is text. Operation is message a model.

17. Search models. Type mini: small models are fast and cheap, and plenty for summaries.

    Small models are fast and cheap, and plenty good for summaries.

18. GPT-4.1-MINI. Choose GPT-4.1-MINI.
19. Write the prompt. Under Message 1, Role is User. Paste the instruction into Prompt.

    Under message one, the role is user.

20. Drag in the email. Drag body from the INPUT to the end of the prompt (here, click it). The preview fills in Jordan's email.

    Here, click it. The preview fills in the first email.

21. Run it. Click Execute step. n8n sends three prompts, one per item.

    n8n sends three prompts. One for each email.

22. Read the answers. 3 items. Each answer is tucked inside output > content > text. The first: *a possible duplicate payment for INV-1042 ... verify our payment records*. Close the node.

    Three items. Each answer is tucked inside output, content, text. The first one says, a possible duplicate payment. Check the payment records. Close the node.

3. Tidy the answer

23. Add a step. Make the result easy to use. Click the + after Message a model.

    Now make the result easy to use.

24. Search for Edit. Type Edit.
25. Edit Fields. Click Edit Fields (Set).
26. Open the earlier node. The INPUT shows the OpenAI answer, but not who sent the email. Expand When clicking 'Execute workflow' below it: earlier nodes are there too.

    The input shows the AI's answer. But who sent the email? Expand the trigger, below it. Earlier nodes are there too.

27. Drop the sender. Drag from onto Drag input fields here (here, click it).
28. Drop the answer. Now drag text (inside content[0]) onto the drop area.
29. Rename it. The new field is called output[0].content[0].text. Select the name and type summary.

    That field name is long.

30. Run it. Click Execute step.
31. One clean row per email. Three items, each with from and summary, ready for a Slack message, a sheet or a daily email. Close the node.

    Three clean items. Who wrote, and what to do. Ready for a Slack message, a sheet, or a daily email. Close the node.

Screenshots

Frequently asked questions

How do I use OpenAI in n8n?

Add the OpenAI node, choose Message a model, connect a credential with your API key (or n8n free credits), pick a model and write a prompt with an expression for the data.

How much does the OpenAI node cost in n8n?

n8n does not charge extra; OpenAI bills your account per call. A short summary with a mini model costs a fraction of a cent.

Do I need an AI agent to use AI in n8n?

No. One OpenAI node with a prompt covers summarising, classifying and drafting. Agents are for jobs where the AI must decide which tools to use.

Start this module free

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Free cheat sheet

Print it or save the PDF: the key steps and checks from this lesson on one page, free.

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Tool cheat sheet Free PDF

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Plain-English definitions, each with an example from a free lesson.

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