30 email subject lines in five styles, with A/B variants and preview text.
The subject line decides whether an email gets opened at all, and generic prompts return 'Quick question' and 'Saw your post'. This tool writes subject lines across six styles (curiosity, urgency, benefit, personal, social proof, contrarian) from a description of your audience and offer, with preview text for each. The paid pack has 30 lines, A/B variants for the top 10 and a short guide to the formulas behind them. The 'expected open rate' it gives is the model's guess, not a measurement: your own test is the only real number.
Brief used: “Sending cold outbound to Heads of Marketing at 50-500 person B2B SaaS companies. Pitching a tool that audits their landing pages and tells them which CTAs are underperforming. First email in a 4-step sequence. List is 200 contacts, I'll send Monday morning. They probably get 60+ cold emails a week. Don't want 'Quick question' energy.”
## Top 5 Shortlist 1. **your /pricing page**: 18 chars, lowercase, looks like an internal note, almost guaranteed open from someone who owns the site. 2. **noticed something on [company.com]**: personal-feeling, specific, implies effort. 3. **3 CTAs on your homepage that aren't converting**: value-stated, specific, no spam words. 4. **was looking at [company.com]: quick thought**: low-effort/personal, lowercase, conversational. 5. **why is the demo CTA below the fold?**: question-format, contrarian, signals you actually looked. ## All 20 (by category) **Curiosity (3)** - noticed something on [company.com]: 33 chars - this might be why your homepage demo CTA underperforms: 50 chars - one thing about your hero: 24 chars **Specific-detail (3)** - 3 CTAs on your homepage that aren't converting: 46 chars - your /pricing page: 18 chars - the headline on [company.com] vs. your competitors: 47 chars **Mutual-connection (2)** (use only if real) - [first name from LinkedIn] mentioned you: 35 chars - following up on [first name]'s intro: 33 chars **Low-effort / personal (3)** - was looking at [company.com]: quick thought (41 chars) - quick one about your landing page: 32 chars - saw your site, one question: 26 chars **Contrarian (3)** - why is the demo CTA below the fold?: 35 chars - your hero headline is hurting conversion: 41 chars - most B2B landing pages have the same 4 mistakes: 47 chars **Value-stated (3)** - 4 specific fixes for your homepage: 33 chars - audited [company.com]: sending the findings (43 chars) - found 4 CTA issues on [company.com]: 35 chars **Question-format (3)** - mind if I send you a 4-min audit?: 32 chars - is the homepage demo CTA intentional?: 37 chars - worth a quick teardown?: 22 chars ## Don't send these (5 the tool rejected) - 'Quick question': generic, every cold email opens this way, marketers ignore it. - 'Boost your conversion rate 3x': contains 'boost', spam-trigger adjacent, unverifiable claim. - 'Free landing page audit!': exclamation + 'free' = filter food. - 'Re: your website': a fake reply. Recipients notice, and it erodes trust in every later email. - 'Hey [first name]': not actually a subject, low effort, screams template. ## Preview-text pairings (top 5) - 'your /pricing page' → 'specifically the comparison table: one thing I'd test.' - 'noticed something on [company.com]' → 'about the demo CTA placement. Worth a quick note?' - '3 CTAs on your homepage that aren't converting' → 'and a specific fix for each. 4 minutes to read.' - 'was looking at [company.com]: quick thought' → 'on the hero section. Want me to send it?' - 'why is the demo CTA below the fold?' → 'genuine question: most B2B sites do this and I think it's wrong.'
Static example. Your own run calls Claude live with your brief.
Founders running cold outbound, sales-led SaaS teams writing manual sequences, agencies running outreach for clients, indie hackers about to email their waitlist. Less useful if you send a handful of emails a week: write those yourself.
The paid pack contains 30 subject lines in six styles (five each), each with preview text and a note on when to use it; A/B variants for the top 10; and a short guide to subject line formulas. It also includes the model's rough open-rate guess per line, which is an estimate to test, not data.
A cold batch is queued for Monday. Get subject lines in several styles so you can split-test three or four across the batch instead of betting on one.
Your list hasn't been emailed in months. Generic 'we're back' subjects can hurt your sender reputation; get re-engagement lines that read like a real person.
1,200 people signed up six months ago and now you're shipping. Get launch subjects that don't read like every other 'We're live!' email in their inbox.
The first email went out and you need different subjects for the next sends that don't feel like the same person shouting louder.
Specific subjects that read like a person wrote them usually do better on cold outbound than generic ones. But open rates also depend on list quality, sender reputation and timing, and mailbox privacy features make open tracking unreliable. Judge your test on replies, not only opens.
Lowercase subjects can look like a forwarded thread or an internal note rather than a marketing blast, which suits outreach between founders and operators. For corporate buyers, test both.
It avoids the obvious set (free, guaranteed, !!!, $$, ALL CAPS, 'act now') and flags lines that combine several of them. It does not run your email through a spam filter: use Mail-Tester or your email platform's preview tool for that.
Pick three or four subjects from different styles, split your batch evenly and send at the same time of day. Compare reply rates as well as opens: a subject with many opens and no replies is misleading. The styles are spread on purpose so you can run this test.
Yes. Say 'email 2 in a sequence' in the brief and you get follow-up patterns (short subjects, a clean 're:' thread, alternatives to 'circling back').