How to Write Transactional Emails With AI in Claude Code

Claude Code can write every email your SaaS sends: the welcome email, the password reset, the receipt and the reminder that a trial ends soon. How good those emails are depends on how you ask. A one-line request gets a generic email. A good brief gets an email that sounds like your product.

This guide shows you how to write transactional emails with AI by briefing Claude Code the way you'd brief a copywriter. Transactional emails are the one-to-one emails your product sends because someone did something, like signing up or paying. You'll see a full example brief and the draft it produces.

What should a good brief to Claude Code include?

A good brief tells Claude Code what the reader just did, who they are, what you want them to do next and how the email should sound. Anthropic's own guidance suggests treating Claude like a smart new colleague who doesn't know your ways of working yet. The more context you give, the better the result.

If you haven't decided which emails you need, start by planning the full set of emails your SaaS needs, then brief them one at a time.

Give the reason behind a rule where you can. "Keep it under 120 words because most people read it on their phone" works better than "keep it short." Claude Code can apply the reason to choices you didn't think to mention.

How do you describe your tone of voice?

Describe your voice in three to five plain words, then show an example of writing you like. Examples steer tone more reliably than adjectives on their own.

Some ways to pin it down:

• Pairs: "friendly, not cute", "clear, not formal", "confident, not pushy".
• Banned words: list any words you never want to see in your emails.
• Samples: paste a few sentences from your website, or an email you were happy with, and say "write like this."
• A person: "like a helpful person at the front desk of a small studio."

If you haven't settled on a voice yet, ask Claude Code to suggest some.

Read the copy on my homepage and suggest three possible tones of voice for my emails. Describe each in three to five words and add a short example sentence. I'll pick the one that fits.

Picking from options is often quicker than describing a voice from scratch.

How do you get a first draft?

Send the whole brief in one message and ask to see a draft before anything is built. Here's a full brief for a welcome email.

Please write the welcome email for my SaaS. It goes out right after someone starts their 14-day free trial. Our users are yoga teachers who run their own classes and are short on time. The one thing I want them to do is add their first class, because that's when the product starts to make sense. Include their first name, the trial length, a button to their dashboard and our support address, help@yourcompany.com. The voice is warm, calm and plain, like a helpful person at the front desk of a small studio. Keep it under 120 words since most people will read it on their phone, with no exclamation marks and no sales talk. Give me two subject line options, and show me the draft before you build anything.

A draft for that brief might look like this:

SubjectYour studio is ready, {first name}

Hi {first name},

Welcome in. Your free trial runs for 14 days, and everything is unlocked.

The best first step is to add one class. It takes a couple of minutes, and once it's in, your students can book straight away.

Add your first class

If anything is unclear, reply to this email or write to help@yourcompany.com.

See you inside, The team at [your product]

The second subject line option might be "Your 14-day trial has started." Read both out loud and keep the one that sounds most like you.

How do you give feedback and ask for changes?

Give feedback the way you would to a copywriter: say what works, what doesn't and why. Specific notes get specific fixes, while "make it better" leaves Claude Code guessing.

Unsure? Ask for options instead of a single rewrite.

I'm not sure about the opening line. Give me three versions, from most formal to most relaxed, and I'll pick one.

When you're happy, tell Claude Code the wording is approved. If you also want the email to look on brand, see how to design your emails with Claude Code.

How do you keep wording consistent across every email?

Ask Claude Code to write a short email style guide and save it in your project instructions. Claude Code reads its project instructions at the start of every session, so anything saved there carries over to every email it writes.

Now that we've agreed on the welcome email, write a short email style guide for my project. Cover our tone of voice, words we use and avoid, how we sign off, and how we write buttons, dates and prices. Add it to your project instructions so you follow it for every email from now on.

A useful style guide covers:

Then brief the rest of your emails against it. You can ask for several at once:

Using our email style guide, write the password reset, payment receipt and trial-ending emails. Show me all three side by side before you build them.

For more messages you can copy, see these 20 things to tell Claude Code to set up your SaaS emails. Changing the wording of a live email later works the same way; see how to update your SaaS emails by asking Claude Code.

What happens once the wording is approved?

Once you approve the wording, Claude Code builds the email into your project and connects it to the right moment, such as a new sign-up. When your SaaS is live, the email goes out from your project automatically. The chat isn't involved.

SimpleSends is a transactional email service built for people who build with Claude Code but don't write code. It connects to Claude Code through a connector, an MCP (Model Context Protocol) server that lets Claude Code work with SimpleSends while you build. With it connected, Claude Code can send you a test copy from the chat, so you see the email in a real inbox before your users do. Before launch, run through how to test your emails before your users see them. For the full journey from planning to sending, see transactional emails in Claude Code.