# Cold Email Subject Lines: How to Write Ones That Get Replies > Good cold email subject lines name the reader's problem in 2 to 5 words. Patterns, 20 examples, follow-up subjects, and why to judge them by replies. Canonical: https://ballast.to/blog/cold-email-subject-lines Last updated: 2026-11-14 A good cold email subject line is 2 to 5 words about the reader's situation, written the way a colleague would write it: "late-stage dropouts", "{{company}} final rounds". It names their problem or their company, never your product, and it promises exactly what the email delivers. Judge it by replies, not opens, because open tracking has been unreliable since Apple Mail started loading images for people who never read the email. ## What does a cold email subject line actually have to do? It has one job: get the right person to read the first line. The subject doesn't sell. A stranger sees your name, which means nothing to them yet, the subject, and the first line of the email as preview text. In that glance they decide whether this is about something they care about or one more pitch. That's why the subjects that work look boring next to the lists of "proven" lines. They read like internal email. "pipeline review", "{{company}} onboarding", "churn after month two". There's nothing to decode and nothing to resent. ## What makes a good cold email subject line? These are the rules Ballast's own Write with AI follows when it drafts a first email, and the checks it runs on what it writes: - **2 to 5 words.** Long subjects get cut on phones and read like a headline. Ballast flags anything over 8 words. - **About the reader, not you.** Name the problem from their side ("missed renewals") or their company with that topic ("{{company}} renewals"). - **Never only your product category.** "payroll software" or "recruiting platform" says you're selling and says nothing about them. Ballast sends a subject like that back to be rewritten. - **Never your company or product name.** The sender name already says who you are. - **Lowercase, except names.** Title Case reads like a newsletter. - **No "Re:" or "Fwd:" on a first email,** and no clickbait questions. A fake reply gets the email opened once and gets your next email deleted. - **True to the email.** In the US, CAN-SPAM requires a subject that matches the content of the message, and it has no exception for business-to-business email ([FTC compliance guide](https://www.ftc.gov/business-guidance/resources/can-spam-act-compliance-guide-business)). A subject that tricks the open breaks the law and the reader's trust in the same move. ## Cold email subject line examples by pattern These are patterns with sample wording, not lines with a claimed open rate. Swap in your reader's real problem; a subject copied from a list reads like one. **The reader's problem, in their words** 1. late invoices 2. churn after month two 3. no-shows on demo calls 4. support backlog on mondays 5. candidates ghosting final rounds **Their company plus the topic** 6. {{company}} renewals 7. {{company}} hiring plan 8. {{company}} onboarding emails 9. {{company}} and spring inventory 10. {{company}} sdr ramp **Something you saw that's specific to them** 11. your pricing page change 12. the new austin office 13. after the series b 14. your talk at saastr 15. the open ae roles Only use these when it's true and you can say it in the first line. **A person who connects you** 16. [name] suggested i write 17. from [name]'s team Only when that person really did suggest it. Naming someone who didn't is the fastest way to make the reader warn their colleagues about you. **A plain question about their world** 18. still running payroll in excel? 19. who owns renewals now? 20. hiring a second sdr? Short and specific, and only when the email answers it. The rule against questions in Ballast's writer is about clickbait ("quick question?"), not about asking something real. ## Which subject lines should you avoid? - **"Quick question", "Partnership idea", "Following up".** They fit any email, so they say nothing. - **A fake "Re:" or "Fwd:".** It implies a conversation that never happened. - **Your product's name or category.** "Introducing Acme" is an ad, and the reader treats it like one. - **Urgency you can't back up.** "Last chance", "only today", "act now" on a first email from a stranger. - **Personalization that's only a token.** "{{first_name}}, a question" shows the reader the mail merge. It doesn't show that you looked at their company. - **A subject the email doesn't deliver.** If the subject says "your pricing page", the first line has to be about their pricing page. Spam-word lists show up in every guide on this, usually without a source. In my experience, what recipients do with your email (reply, delete, report it as spam) matters far more than any single word, so a clean subject on an email people report as spam still ends up in spam. The [guide to why emails go to spam](https://ballast.to/blog/why-emails-go-to-spam) covers what actually moves placement. ## What subject line should a cold email follow-up use? None of its own: send follow-ups as replies in the same thread, with "Re:" and the first email's subject. The reader then sees your first email under the follow-up and doesn't have to remember who you are. Here "Re:" is honest, because it really is a reply to your earlier email. To thread properly, a follow-up needs more than a copied subject. Gmail and Outlook group messages into a conversation using the In-Reply-To and References headers, which point at the first email's Message-ID. Ballast threads every step after the first by default, with "Re:" plus the subject the lead actually received, including a spintax or A/B variant. Start a new thread only when you change the subject for a reason: a new angle that needs its own subject, or a last email to a different person at the company. More on timing and wording in [cold email follow-ups](https://ballast.to/blog/cold-email-follow-up). ## How should you test cold email subject lines? By replies, and with enough emails to tell a real difference from luck. Open rates can't judge a subject anymore. With Apple Mail's Protect Mail Activity turned on, remote content (including a tracking pixel) is downloaded privately in the background when the email arrives, not when the person views it ([Apple Mail User Guide](https://support.apple.com/en-za/guide/mail/mlhl03be2866/16.0/mac/26)). Every email delivered to those readers counts as opened, read or not. On top of that, a tracking pixel is one more thing for a filter to notice in a first email from a stranger. Ballast leaves open tracking off by default for that reason. Replies are the number that means someone read it. They're also rare, so a test needs volume: 1. **Change only the subject.** Same body, same list, same days, or the result tells you nothing. 2. **Send each version at least 100 times** before you read anything. With reply rates in the low single digits, a 2-versus-4 reply gap on 50 sends each is noise. 3. **Look for a clear gap.** Ballast's automatic A/B winner, when you turn it on, only turns a variant off when both have 100 emails, the leader has at least 5 replies, and the leader is at least 95% likely to get more replies. Until then it keeps sending both. 4. **Count positive replies separately.** A clever subject can draw "please remove me" replies. That's a reply, not a win. ## Does the preview text matter in a cold email? Yes, as much as the subject. In a plain cold email there's no hidden preheader: the preview is the first line of the body. If it's "Hope you're doing well" or "My name is Alex and I work at...", the subject has done its job and the first line undoes it. Make the first line carry on from the subject. Subject "late invoices", first line "Saw you're hiring a second AR clerk at {{company}}. Usually that means invoices are slipping past 60 days." The two together should read like one thought. ## FAQ ### How long should a cold email subject line be? 2 to 5 words is a good range for a first email. It fits on a phone without being cut and reads like a note rather than a headline. Ballast's writer aims for that range and flags subjects over 8 words. ### Should cold email subject lines be lowercase? Lowercase, except names, is a good default. It reads like an email from a person. Title Case and all caps read like marketing. ### Should I put the prospect's first name in the subject line? Only if it adds something. A first name alone is the most common mail-merge token, so readers ignore it. The company name with a topic ("{{company}} renewals") shows you know who they are and why you're writing. ### Is it OK to use "Re:" in a cold email subject line? On a follow-up in the same thread, yes: it's a real reply to your first email. On a first email, no. It implies a conversation that never happened, and in the US a misleading subject also breaks CAN-SPAM. ### How do I know if a subject line is working? Count replies, and positive replies separately, on at least 100 sends per version. Apple Mail inflates open rates, so a subject with more opens isn't the better one if it gets fewer replies. ### Can AI write my cold email subject lines? It can draft them, if you give it the reader's real problem. Left alone, models tend to write the product category ("AI sales tool") or a generic hook. Ballast's Write with AI gets the problem from your offer profile and rewrites any subject that only names what you sell.