The task
You are sending a campaign email and you want a higher open rate than last week’s. You need 5 subject lines worth A/B-ing, a body short enough that someone reads it on a phone in line at a coffee shop, and a CTA the reader can act on without thinking. The actual constraint is the inbox preview pane: subject + preview text together must earn the click.
When AI helps — and when it does not
AI is very good at subject-line ideation and tone tuning. It is poor at understanding what your list actually responds to. That comes from your last 10 campaigns’ open rates. Use AI to generate; use your own click history to choose. AI should never invent an offer, urgency claim, or scarcity (“only 3 left!”) that you cannot back up.
What to feed the AI
- Audience and their last interaction (signed up last week, dormant 90 days, repeat buyer)
- The offer or news (what is actually new for this reader)
- Primary CTA (single, specific verb: Shop, Read, Reserve, Reply)
- Brand voice in one sentence (“warm, direct, no exclamation marks”)
- Any compliance constraints (financial, health, regulated industry language to avoid)
- Last 3 subject lines that worked, and 3 that did not, so AI knows your audience’s pattern
Copy-ready prompt
Write a marketing email.
Audience and last interaction: <segment, recency>
Offer / news: <line>
Primary CTA verb: <Shop / Read / Reserve / Reply>
Brand voice: <one sentence>
Compliance constraints: <avoided language>
Subject lines that worked: <last 3>
Subject lines that did not: <last 3>
Return:
1. Five subject line candidates, each under 50 characters. Mix: curiosity, news, benefit, question, low-key. Mark which is closest to past winners.
2. Preview text (35-90 chars) for each subject — must extend the subject, not repeat it.
3. A 150-200 word body. Mobile-first: short paragraphs, one idea per paragraph, scannable.
4. Button text (2-3 words) and a one-line fallback link.
5. A short "if low open rate" alternate subject + preview pair to send as a resend to non-openers.
Do not invent scarcity, deadlines, or testimonials. If you would write "limited time," write [VERIFY: real deadline?] instead.Variant for transactional-adjacent emails (shipping update plus upsell): “Same task but the email must clear that this is a shipping update first; promo is secondary and clearly labelled.”
Recommended output structure
Subject + preview pair (5 of them), then body with one paragraph per idea, then a single button. Avoid stacked CTAs. Preview text is a copywriting surface, not a tagline; treat it as line two of the subject.
How to check the output is usable
- Read the subject + preview together in the same line. Does it earn the click without seeing the body?
- Body has one CTA. If you find two, kill the weaker one
- The body sounds like one human writing to one human, not a brand to a list
- No invented scarcity, fake testimonials, or unverifiable claims
- Test in Litmus or a phone preview. Anything cut off in iOS preview is a problem
Common mistakes
- Clickbait subject with thin body. Opens once, unsubscribes after two
- Stacking 3 CTAs because “people want choice”. They want one obvious action
- Letting AI write fake urgency (“ends tonight!”) that contradicts your real merchandising
- Skipping the preview text. Leaving “View this email in your browser” as the preview line throws away 60 characters of conversion surface
- A/B testing too small a list. You need ~1,000 opens per arm before the difference means anything
Practical depth notes
For How to Use AI to Write Email Marketing Copy: Subject Lines, Body, and Single CTA, the difference between a usable AI result and a generic one is the input packet. Give the model the audience, the current draft or raw material, the desired format, the decision you need to make, and two examples of what good and bad output look like. Ask it to preserve facts first, then improve structure or wording second.
After the first response, do a separate review pass. Look for missing constraints, invented details, weak calls to action, and language that sounds plausible but does not match the real situation. The best final output should be easy to use immediately: clear owner, clear next step, and no hidden assumption that someone else has to untangle.
FAQ
- Subject A/B or content A/B? Subject first: bigger swings, faster signal. Body A/B only after subject is fixed.
- How long should the body be? As long as it earns. Newsletters can be 400 words; promo emails should be 100-200.
- Should AI write the unsubscribe footer? No. That is a legal text in most jurisdictions. Copy yours verbatim.
Related
- Email marketing prompts — additional phrasings and segment-specific variants
- Email subject line prompts — dedicated subject-line generator
- Abandoned cart email prompts — when the campaign is a recovery sequence
- AI newsletter tutorial — full newsletter workflow
- AI email triage tutorial — managing incoming, not outgoing, email