Build a Custom GPT That Writes Sales Follow-Up Emails

Ask plain ChatGPT for a follow-up email after a demo and you get emojis, all caps and a limited time offer nobody approved. In this free lesson you build a sales follow-up writer for Northwind Scheduling Software: a Custom GPT that knows the product, the plans and your team's rules, and writes a short email a prospect might actually answer.

What you will build: a sales follow-up email writer

You start by giving ordinary ChatGPT one bare prompt: write a follow-up email to a prospect after our sales demo. The reply is the email every buyer deletes. The subject line shouts about an amazing opportunity. The body promises to revolutionize the business, talks about crushing the competition, and ends with a limited time offer and 'just checking in'. There is nothing from the demo in it.

Then you build a Custom GPT called Sales Follow-Up Writer. You give it written rules and a sales playbook, and you send the exact same prompt again. This time you get a plain subject line, one line of thanks, three short bullets on the features that fit the prospect, the Team plan price at $39 per user per month because the prospect asked, and one next step: a 14-day free trial set up on a 20-minute call, with two specific times to choose from.

Who this is for

This lesson is for sales reps, account executives, SDRs and sales managers who write the same kinds of follow-ups every day. After a demo, after a trial, after a prospect goes quiet. You do not need any AI experience or technical background. If you can copy and paste, you can build this.

Step by step: what you do in the lesson

• Ask ChatGPT: paste the bare follow-up prompt, send it, and read the generic reply.
• Explore GPTs: open More in the sidebar, click GPTs, then Create to open the GPT builder.
• Name your GPT: call it Sales Follow-Up Writer.
• Add instructions: paste the follow-up rules for Northwind Scheduling Software. They set the tone, the email layout, the pricing rules and what the company sells.
• Upload knowledge: open Google Drive, preview Northwind-Sales-Playbook.pdf, scroll through it and click Select to attach it.
• Test your GPT: paste the same prompt word for word into the preview and compare the result.

What goes into the rules and the sales playbook

The instructions read like a brief for a new rep. Sound like someone who listened on the call, not a pushy salesperson. No emojis, no all caps, and none of the pressure phrases: act now, limited time, don't miss out, last chance. Every email gets a subject under 8 words, one line of thanks, a 2 to 3 bullet recap of the features that match the prospect's need, a price only if they asked, and exactly one next step with a clear ask. Under 150 words.

The content rules keep the email honest. Only mention features and prices from the playbook, and never invent a discount. If a detail is missing, like the prospect's first name, the GPT leaves a [bracket] for the rep to fill in instead of guessing. It never promises results like 'double your bookings' and never talks down other products.

The playbook PDF holds the facts: who Northwind sells to (service businesses with 2 to 50 staff), the features (online booking, reminders, a shared calendar, recurring jobs, simple reports), the three plans at $19, $39 and $59 per user per month, the 14-day free trial, the follow-up rules, and a sample email.

Why it works

Plain ChatGPT has never seen your product or your price list, so it fills the gap with the loudest sales copy it knows. A Custom GPT carries your rules and your playbook into every chat, so you stop re-explaining the product each time. The rules also stop the mistakes that cost deals, like a price that is not on the sheet or a promise the product cannot keep.

Common follow-up mistakes this avoids

• The empty check-in. 'Just circling back' gives the prospect nothing to answer. Every email here recaps what they said and asks for one thing.
• Pressure. Fake deadlines and all caps make a small business owner stop replying. The rules ban them.
• Made-up numbers. The GPT quotes only the plans in the playbook, so no rep promises a price finance never approved.
• Too long. A 150-word limit keeps the email readable on a phone between jobs.

How to use this on your sales team

Swap in your own playbook, price sheet and two or three follow-ups that got replies. Then paste your call notes, the prospect's name and what they cared about, and let the GPT draft the email while you check the details. Share the GPT with the team so every rep starts from the same rules and the same prices. It works for post-demo recaps, trial check-ins and re-engaging deals that went quiet. You still read every email before you send it.

Frequently asked questions

How does the interactive lesson work?

Each step is shown to you first on the left (Watch). Then you do it yourself in a practice copy on the right (Your turn), and every click is checked. If you get stuck, press Do it for me. It is a practice copy, so no real accounts are touched.

Is this lesson free?

Yes. Stepthrough is completely free. To build the GPT for real you need your own ChatGPT account, and creating Custom GPTs may require a paid ChatGPT plan.

Will the Custom GPT make up prices or discounts?

The instructions tell it to use only the prices in your playbook and never invent a price or a discount. You should still check every email before it goes out.

What if I do not have the prospect's details?

The rules tell the GPT to leave a [bracket] for anything missing, like a first name or team size, so you can fill it in rather than send a guess.

Can my whole sales team use the same GPT?

Yes. A Custom GPT can be shared, so every rep writes from the same rules and the same playbook. Check your ChatGPT plan's sharing options.

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