Email Copy
The subject line determines whether the email exists. The body determines whether the click happens. Here's how to write both.
The same list. Two subject lines. A 34-point difference in open rate.
A SaaS company sends their weekly newsletter to 22,000 subscribers. In a moment of curiosity, their marketer runs an A/B test on the subject line.
Version A: "August Product Update: New Features and Improvements" Open rate: 14.2%
Version B: "The thing our power users do that most people miss" Open rate: 48.1%
Same list. Same email body. Same send time. Same product. One subject line treated the email like an announcement. The other treated it like a secret.
3,100 extra people opened that email and saw the product update — just because of the subject line. Email marketing is widely cited as the channel with the highest ROI in digital marketing (based on Litmus State of Email and DMA annual research; figures vary significantly by methodology, industry, and list quality — consult the current editions for updated benchmarks), but that ROI is completely inaccessible if nobody opens the email.
The subject line is not a label. It's a promise, a tease, a hook — and it is the most important piece of copy in any email.
Subject lines: the inbox is a competition
Every email in someone's inbox is competing for the same limited attention. Most inboxes have 20–100 unread emails. Your subject line needs to win against all of them — in the 2–3 seconds someone spends scanning the list.
What makes a subject line work:
The 6 subject line formulas:
| Formula | Example | Why it works |
|---|---|---|
| The curiosity gap | "The thing our best customers do differently" | Creates an itch the reader must scratch |
| The number | "7 subject line mistakes killing your open rates" | Specific, scannable, promises clear value |
| The question | "Are you making this pricing mistake?" | Reader answers internally — they're already engaged |
| The personal | "Quick question" / "Saw this and thought of you" | Low friction, conversational, stands out in inbox |
| The direct | "Your invoice is ready" / "Your free guide is here" | Zero ambiguity — works for transactional emails |
| The urgency | "Offer closes tonight" / "Spots filling up" | Real deadlines drive action; fake ones erode trust |
What kills subject lines:
- All caps: "HUGE SALE HAPPENING NOW" — triggers spam filters and feels like shouting
- Excessive punctuation: "Amazing offer!!!" — spam signal
- Spam trigger words: free, guarantee, no risk, winner, urgent, act now — use with caution
- Vague promises: "Important update" — could be anything, implies nothing interesting
- Long: Most inboxes show 40–60 characters on mobile. Keep it under 50 characters.
Preview text: The greyed-out text that appears after the subject line in most email clients. It's a second subject line — use it. Don't let the email client default to "View in browser" or the first line of your email.
Subject line: "The thing our power users do that most people miss" Preview text: "It's not a feature. It's a habit that takes 5 minutes a day."
Using AI for subject lines: Prompt: "Write 15 subject line variations for this email: [summarise the email content]. Use these formulas: curiosity gap, number, question, personal tone, direct, urgency. Keep each under 50 characters. Also write a preview text for each one." Generate 15, pick your top 3, test them.
Subject Line Workshop
25 XPEmail body: the one-idea rule
Once the email is opened, most copywriters make the same mistake: they try to say everything.
The golden rule of email copy: one email, one idea, one CTA.
Emails that cover three topics get a third of the engagement of emails that commit fully to one. The reader's attention is scarce. Every link you add after the first one reduces clicks on the first one. Every idea you add after the first one dilutes the first one.
Pick your one idea. Cut everything else.
The structure of an email that gets clicked:
Length: Shorter is almost always better for marketing emails. The goal is the click, not the read. Get to the point, bridge to the CTA, and get out. If you need to share a lot of information — put it in the article/page you're linking to.
Exception: newsletters with multiple stories or digest formats, where the email IS the content. Even there, short intro paragraphs per story work better than essays.
Writing the email body
Treat it like a text message from a knowledgeable friend.
The most effective marketing emails don't sound like marketing emails. They sound like they're from a real person who knows something useful and is sharing it because they think you'll find it valuable.
Compare:
Corporate:
"Dear Valued Subscriber, We are pleased to present this week's curated insights for marketing professionals. Our team has assembled a comprehensive overview of the latest industry developments..."
Human:
"Something clicked for me last week.
I've been tracking which email subject lines get the best open rates for the past six months. I expected the 'curiosity gap' headlines to win. They did — but not by the margin I expected.
The surprising winner? Subject lines under 30 characters. Short, specific, almost casual.
I wrote up everything I found, with examples and the data. You can read the full breakdown here: →"
Same information. Completely different feel. One person skims and archives. The other person actually clicks.
The techniques:
| Technique | What it does | Example |
|---|---|---|
| Second person | Puts the reader in the story | "You've probably noticed..." not "Marketers often..." |
| Short sentences | Creates rhythm and pace | "It worked. Surprisingly well." |
| Line breaks after every sentence | Forces scannable format | Each sentence gets its own line |
| Conversational openers | Feels like a message, not a broadcast | "Quick thought." / "Something I noticed." / "Honest question:" |
| Specificity | Makes claims believable | "28% raise" not "significant salary increase" |
Using AI for email body: Paste your notes or rough points into Claude and prompt: "Write an email body from these notes. Tone: conversational, like a knowledgeable friend texting someone they respect. Short paragraphs (1–2 sentences each). One idea, one CTA. No corporate language. Email should be under 200 words." Then edit the output for your own voice.
There Are No Dumb Questions
"Should I personalise emails with the subscriber's first name?"
First-name personalisation in the subject line used to significantly lift open rates. Today it's so overused that it's neutral at best. More impactful personalisation: segment your list and send different content to different groups (new subscribers, active buyers, people who clicked a specific link). Behaviour-based personalisation outperforms name-based personalisation.
"How often should I email my list?"
Consistently. The biggest mistake isn't sending too often — it's being inconsistent. A weekly email that people expect and enjoy builds more trust than sporadic emails whenever you have something to sell. A daily email can work if the content is genuinely worth it. Find a cadence you can sustain with quality, and stick to it.
Rewrite the Corporate Email
25 XPTransactional vs. marketing emails
Not all marketing emails are newsletters or promotions. Transactional emails — order confirmations, password resets, receipts, shipping notifications — have historically reported the highest open rates of any email type (50–80% (upper end of historical pre-2021 ranges; figures vary widely by email type and platform), noting that figures since Apple Mail Privacy Protection launched in 2021 are inflated by pixel pre-loading — treat as directional), because they contain information the customer needs.
This makes them prime real estate for marketing copy — but most companies waste them with bare-bones templates.
| Transactional email | Marketing opportunity |
|---|---|
| Order confirmation | Upsell related products, invite to loyalty programme |
| Shipping notification | Build excitement, share brand story, invite to follow on social |
| Welcome email | Deliver on the promise that got the signup, set expectations, make first CTA low-friction |
| Abandoned cart | Name the specific product, reduce friction, offer help |
| Receipt | Ask for a review at exactly the right moment |
The welcome email is the most important email you'll ever send. It's opened by more people (50–70% open rate (pre-2021 benchmark estimates; higher-quality sources reported up to 80% for small, highly engaged lists — treat as directional) — treat as directional, as Apple Mail Privacy Protection since 2021 inflates open rate figures industry-wide) than any other email in your sequence. It sets the tone for the entire relationship. Yet most welcome emails are: "Thanks for signing up. Here's your free guide. Talk soon."
A great welcome email: delivers the lead magnet immediately, tells the reader what to expect, makes a low-friction first CTA (read one post, answer one question), and feels personal.
Write a 3-Email Welcome Sequence
50 XPBack to the two subject lines
Version A — "August Product Update: New Features and Improvements" — told the reader exactly what was inside and gave them no reason to open it. If they weren't already curious about the product update, they had nothing to gain. Version B — "The thing our power users do that most people miss" — created a curiosity gap: it implied that some people already know something valuable, and the reader might not be one of them. That asymmetry is what drove a 34-point lift in open rate. The specificity of "power users" also did quiet work — it made the email feel like insider knowledge rather than a broadcast. The body content was identical in both versions, which proves the point cleanly: the subject line is not a label for what's inside. It's a reason to open. Write it last, treat it as its own piece of copy, and test it as aggressively as you'd test any ad.
Key takeaways
- The subject line is 80% of the email. If it doesn't get opened, nothing else matters. Use curiosity, specificity, or personality — avoid vagueness and spam triggers.
- One email, one idea, one CTA. Emails that try to cover everything get ignored. Commit to a single idea and a single action.
- Write like a knowledgeable friend, not a corporate broadcast. Short paragraphs, second person, specific details, conversational openers.
- Transactional emails generate significantly higher open rates than marketing emails (commonly cited around 3×, though reported rates are inflated by Apple Mail Privacy Protection since 2021) — they're the most underused copywriting opportunity in most businesses.
- The welcome email is the most important email you'll ever write. Treat it accordingly.
Knowledge Check
1.An email with the subject line 'August Newsletter: Company Updates and Industry News' gets a 12% open rate. The same list gets a test email with the subject 'The mistake 80% of marketers make in August' — open rate 41%. What is the primary reason for the difference?
2.A marketer sends an email about a new product launch that includes: an announcement of the product, a 20% discount offer, a link to a webinar, a request to follow the brand on Instagram, and a link to a blog post about the product category. What is the most significant problem with this email?
3.Why do transactional emails (order confirmations, shipping notifications, welcome emails) represent an underused marketing opportunity?
4.A welcome email currently reads: 'Thanks for signing up! Here's your free guide. We'll be in touch. Best, The Team.' What is the most impactful improvement?