Cold email subject lines
last updated: Sep 24, 2025
TL;DR
Most opens are won or lost in the subject line. Use plain, specific lines tied to a pain or referral, keep most under ~45 characters, and run a 7-day test. Before clever copy, make inboxes trust you: set up SPF DKIM DMARC and include a visible unsubscribe link in the footer and the List-Unsubscribe header. This page includes 25 cold email subject lines you can use now.
How to:
How to:
- Set up SPF DKIM DMARC and add an unsubscribe link.
- Draft 15 lines across demo, referral, pain. Run A/B testing subject lines for 7 days.
- Keep winners, rotate losers. Re-test monthly.
Glossary
- SPF: DNS record listing allowed senders.
- DKIM: Cryptographic signature proving integrity.
- DMARC: Policy for handling auth failures.
- List-Unsubscribe: One-click unsubscribe header.
- Open rate: Opens divided by delivered emails.
- Reply rate: Replies divided by delivered emails.
- Preheader: Preview text beside the subject.
- Personalization: Using name or company details.
- Throttling: Limiting daily sends for safety.
How to A/B test different subject lines on your cold email
- Make inboxes trust you. Set up SPF, DKIM, and DMARC. Align your From domain. Add a List-Unsubscribe header and a visible footer unsubscribe link. This protects deliverability and makes testing reliable.
- Pick one intent. Choose demo, referral, or pain-point for this test round. One intent per sequence keeps signals clean.
- Draft 15 short options. Five per intent. Promise one clear outcome. Put the core value in the first 33 characters for mobile.
- Set a simple test. Randomly split the same list. Aim for 50+ recipients per variant. If volume is low, rotate variants across days.
- Control everything else. Same sender, copy, and send time. Change only the subject.
- Score replies first. Opens are noisy in B2B cold email. Prioritize reply rate and positive reply rate.
- Roll forward fast. Keep the top 1–2. Park the rest. Re-test monthly on fresh leads.
Benchmarks
Sample math.
You send 1,000 emails at $0.40 each. Open rate 35% → 350 opens. Reply rate 7% → 70 replies. Positive replies 3% of delivered → 30. If 50% become SQLs, you get 15 SQLs. Cost per SQL = $400 ÷ 15 = $26.67.
You send 1,000 emails at $0.40 each. Open rate 35% → 350 opens. Reply rate 7% → 70 replies. Positive replies 3% of delivered → 30. If 50% become SQLs, you get 15 SQLs. Cost per SQL = $400 ÷ 15 = $26.67.
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Subject line strategy
- Default to benefit. If buyers know the category and pain, state a concrete outcome. Example: “Cut SOC 2 prep to 7 days”.
- Use curiosity when fatigued. Switch if benefit lines stall. Keep it honest. Example: “Quick question about your churn trend”.
- Match the inbox moment. Tie to a trigger the lead recognizes: a launch, a hiring push, a comment on their post, or a new integration.
- Let the email deliver proof. The subject makes a promise. The first sentence delivers the proof or context.
- Borrow trust. After a referral or event touch, curiosity lines work better because context exists already.
25 cold email subject lines you can use
Demo intent
Referral intent
Pain-point intent
Bad → good rewrites
- Quick demo for {{company}}’s {{goal}}
- Show you in 7 minutes?
- Can I prove this in a week?
- Worth a 10-min screen share?
- {{first_name}}, 2 slides on {{metric}}
- Fast walk-through this week?
- Should I book 15 on Thu?
- If I miss, I’ll stop asking
- Short demo. Real numbers.
Referral intent
- {{referrer}} suggested I reach out
- From {{mutual_contact}} re: {{topic}}
- {{first_name}}, quick intro via {{referrer}}?
- Following up from {{event}}
- Saw your post on {{channel}}
- Intro from {{partner}} for {{company}}
- Per {{referrer}}’s note yesterday
Pain-point intent
- Renewals slipping after Q2?
- SOC 2 prep keeps slipping?
- QA cycles blocking this sprint?
- SDR replies stalling at 3%?
- Drop-offs at onboarding step 2?
- Seeing churn after the paywall change?
- Ops costs creeping up this quarter?
- Procurement stuck on security review?
- NPS looks fine, but tickets up?
Bad → good rewrites
- ACT NOW. LIMITED-TIME OFFER!!! → 2 lines to save 6 hours
- Make $$$ FAST with AI → Cut L1 tickets with AI triage
Risks
- Words vs reputation. Spam words matter less than authentication and engagement. Avoid exaggerated claims anyway.
- Truncation. Long subjects get cut on mobile. Lead with value in the first 33 characters.
- Missing unsubscribe. Lack of an easy unsubscribe hurts deliverability. Add a footer link and the List-Unsubscribe header.
- Speed. Sending too fast from a new domain can trigger blocks. Warm up and throttle.
FAQ
- You:Do emojis help in B2B subjects?Guide:Use sparingly. Test only if your buyer uses them.
- You:Where should I put personalization?Guide:Front load it when it adds value. Example: “{{first_name}}, 2 slides on churn”.
- You:Does time matter?Guide:Fit matters more. If equal, mid-morning mid-week is a safe default.
- You:Can I test with low volume?Guide:Yes. Rotate variants across days and aggregate 200–300 sends before choosing..
- You:What about preview text?Guide:Use it to complete the promise from the subject.”
- You:Legal must-haves for cold outreach?Guide:Identify the sender, add a postal address, and include easy unsubscribe plus a List-Unsubscribe header.
Ready to stop guessing?
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