What works
Good cold subject lines look like an email from a person, not a campaign:
- Short — two to five words.
- Specific — their company, their city, their product.
- Plain — no exclamation marks, no emoji, no ALL CAPS.
- Honest — the email must deliver what the subject promises.
Examples for local businesses
- "Carter Plumbing on Google"
- "question about your reviews"
- "website for Greenline"
- "Denver HVAC search"
- "your booking page"
- "idea for Bright Smiles"
- "photos on your Maps listing"
- "quick one, Maria"
Examples for creators
- "your espresso video"
- "sponsorship — Grindwell"
- "editing for {Channel}"
- "collab idea"
- "thumbnail test?"
Examples for SaaS founders
- "Notely after launch"
- "Formly at $8K MRR"
- "comparison pages for Taskbird"
- "support for small SaaS"
- "your onboarding flow"
Examples for advertisers
- "your March ads"
- "new hooks for Pawsome"
- "landing page for your offer"
- "UGC test?"
Mistakes to avoid
- Fake replies ("Re:" or "Fwd:" on a first email) — it destroys trust.
- Clickbait that the email doesn't pay off.
- Spammy words used aggressively ("free!!!", "guaranteed", "act now").
- Personalisation that breaks — "Hi {{firstName}}" in the subject when the field is empty. Set fallbacks.
Test properly
Change one thing at a time and test on at least a few hundred sends per variant. Open rates are less reliable than they used to be because of privacy features, so judge subject lines by replies too.
Pair with a matching first line
The preview text is the first line of your email. Make it continue the subject: subject "Carter Plumbing on Google", first line "Searched 'emergency plumber Denver' and you're 6th…".