Verified against ChatGPT · 2026-07-05
Generate email subject lines for a campaign send, sized for the inbox
Get subject line variants for a specific email send, each checked against mobile truncation, spam-trigger language and the preview text pairing — not just a list of clever lines.
The prompt
Ready to copy — highlighted parts are example details you can swap.
Email purpose: Get past customers who haven't ordered in 90 days to use a 15% comeback discount before it expires Friday. Audience: Lapsed customers of a D2C skincare brand, mostly opened emails before but haven't purchased in 3 months. Key detail that must appear or be clearly implied: 15% off, code COMEBACK15, expires this Friday. Brand voice: Warm and a little playful, never uses ALL CAPS or excessive urgency language. Write 8 subject line variants, each ≤45 characters (so it doesn't truncate on most mobile inboxes), plus a matching preview text (≤90 characters) for each — the preview text should add information, not just repeat the subject line. Group them into: 2 curiosity-led, 2 benefit/offer-led, 2 urgency-led (real urgency only — the offer actually expires, don't manufacture false scarcity), 2 plain/direct. Flag any variant that risks landing in spam or promotions due to language patterns (excessive punctuation, "free," all-caps words, too many emoji) so I know which ones are riskier to send even if they'd perform well on open rate alone.
Customize the highlighted detailsoptional — the prompt above already works
Why this works
Subject lines are judged almost entirely by inbox preview, so a 'great' line that truncates at character 38 or duplicates its own preview text is invisible value. Testing across four distinct psychological angles, rather than eight variations of one hook, is what makes a subject-line test actually informative, and flagging spam-trigger language upfront prevents optimizing for an open rate that never reaches the inbox in the first place. The false-urgency guardrail matters because manufactured scarcity is both a deliverability risk and, in several markets, a regulated deceptive-marketing practice.
What you get back
Curiosity: "We kept your seat warm" / Preview: "One reason we think you’ll be back this week." Benefit: "15% back, no strings" / Preview: "Same products, same you, less on the bill." Urgency (real): "Ends Friday: your 15% is waiting" / Preview: "Code COMEBACK15, expires midnight Friday." Flagged risk: any variant using "FREE" in caps or 3+ emoji is more likely to route to Promotions.
Verified against
ChatGPT GPT-5.1 · 2026-07-05
Claude Claude Sonnet 4.5 · 2026-07-06
Changelog
- 2026-07-06 — Initial version.
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