Cold Email Subject Lines: Principles and 50 Examples by Situation

A good cold email subject line is short, specific to the person, honest about what's inside, and looks like it came from a human rather than a campaign. Think "question about [Company]'s hiring", not "🚀 Unlock 10x Growth Today!" Below are the principles, then 50 example lines sorted by situation.

You won't find open-rate statistics in this post. Most figures quoted online for subject lines come from vendors that don't publish their method, and open rates themselves are now unreliable (more on that below). What you will find is what mailbox providers and the law say about subject lines, and examples you can adapt.

The rules that aren't optional

Two sets of rules apply to every subject line: the mailbox providers' guidelines and, for US recipients, the CAN-SPAM Act. Both are about honesty.

Google's email sender guidelines say: "Message headers and message content should be accurate, and not misleading or deceptive." They also say specifically: "don't send messages with subject lines starting with Re: or Fwd: unless the messages are actual replies or forwards." And: "Don't use emojis or other non-standard characters to imitate graphic elements in messages, with the intent to deceive or influence recipients."

The FTC's CAN-SPAM compliance guide is direct: "Don't use deceptive subject lines. The subject line must accurately reflect the content of the message." Our post on CAN-SPAM and cold email covers the rest of the Act.

So the fake "Re:", the invented "Following up on our call" to someone you've never spoken to, and the "Your invoice" that's actually a pitch are all out, even before considering how recipients react to them.

Principles that hold up

A cold subject line has one job: to make the right person open a message from a stranger without feeling tricked. These principles follow from that.

1. Be specific to them. A company name, a role, a recent event or a mutual connection signals the message was written for this person. Generic lines read as bulk mail.
2. Keep it short. Mail apps truncate subject lines differently, especially on phones. Put the words that matter first.
3. Write like a colleague. Internal emails tend to be lowercase, plain and brief: "quick question", "intro", "Thursday?". Marketing subject lines tend to be title-case and full of adjectives. Cold email should look like the first kind.
4. Match the body. If the subject promises a question, the first line should ask it. A mismatch feels like bait and costs trust on the next email too.
5. Skip the tricks. Fake urgency, ALL CAPS, misleading emojis and invented familiarity are what spam reports are made of.
6. Don't obsess over trigger words. Single words like "free" carry little weight in modern filtering compared with reputation and complaints. See do spam trigger words still matter.

50 examples by situation

Pick the situation first, then adapt the line. Replace the brackets with something real; a line with a generic placeholder left in it is worse than no personalisation at all.

Asking a direct question

1. question about [Company]'s [process]
2. [Name], quick question
3. who handles [area] at [Company]?
4. are you the right person for [topic]?
5. how are you handling [specific problem]?
6. [Company] + [your category]?
7. still using [tool they use]?
8. worth a look for [team]?

Referencing something they did

9. your post on [topic]
10. saw [Company]'s [launch/news]
11. congrats on [new role/funding/milestone]
12. loved your talk at [event] (only if you were there)
13. [Company]'s new [product/location]
14. your hiring for [role]
15. noticed [specific observation about their site/product]

Mutual connection or referral

16. [Referrer] suggested I reach out
17. intro via [Referrer]
18. [Referrer] mentioned you
19. fellow [community/school/group] member
20. met [colleague] at [event]

Leading with the problem

21. [problem] at [Company]
22. cutting [cost/time] on [process]
23. [number] [unit] of [task] a week
24. fixing [specific pain point]
25. [team] spending too long on [task]?
26. the [process] bottleneck
27. idea for [Company]'s [goal]

Leading with relevance or proof

28. how [similar company] handled [problem]
29. what worked for [peer type] teams
30. [industry] teams and [problem]
31. a [timeframe] fix for [problem] (only if true)
32. for [role]s dealing with [problem]

Only cite a company or result you can stand behind. An invented case study in a subject line is a deceptive subject line.

Short and plain

33. quick idea
34. intro
35. [Company]
36. [Name]
37. thoughts?
38. 15 minutes next week?
39. Thursday?
40. one question

These work best when the body follows up with something specific straight away. A vague subject plus a vague body gets deleted.

Follow-ups

Follow-ups usually belong in the same thread, so they keep the original subject. When you do start a new thread:

41. one more thought on [topic]
42. a different angle on [problem]
43. [resource] for [Company]
44. closing the loop
45. should I stop reaching out?

For the body copy, see follow-up email templates.

Re-engaging an old conversation

46. picking up from [month]
47. back to [topic]
48. you said to check back in [month]
49. any change on [project]?
50. [Company] and [topic], take two

Use these only if there really was a previous conversation. Otherwise it's a new first email and should read like one.

Lines to avoid

If a subject line would make the reader feel misled once they open the email, don't send it.

• "Re:" or "Fwd:" on a first email. Explicitly called out in Google's guidelines.
• Invented familiarity: "Following up on our call", "As discussed", "Great chatting yesterday".
• Fake transactional lines: "Your invoice", "Account update", "Order confirmation".
• Hype and urgency: "LAST CHANCE", "Don't miss this", "Urgent".
• Emoji used as a gimmick, and decorative symbols that imitate graphics.
• Unfilled or obviously automated personalisation: "Hi {first_name}", or a company name with "Inc." and odd capitalisation pulled straight from a database.

How to test subject lines honestly

Compare subject lines on replies, not opens. Open tracking counts image loads, and Apple's Mail Privacy Protection "downloads remote content in the background by default — regardless of whether you engage with the email." A subject line can look like a winner on opens because more of its recipients use Apple Mail. Open tracking can also cost you deliverability; see does open tracking hurt cold email deliverability.

A fair test looks like this:

1. Change only the subject line. Same body, same list segment, same sending inboxes, same days.
2. Split randomly, not by list order, which often clusters by company or source.
3. Count positive replies, and record removal requests and complaints alongside them.
4. Wait for enough results. If each version gets a handful of replies, the difference is probably noise. Keep going or treat the result as a hunch.
5. Retest winners on a fresh segment before rolling them out everywhere.

The subject line can't fix a bad list

If the address doesn't exist, the subject line is never seen. A bounce on a cold sequence also counts against the sending domain, and enough of them push your good emails toward spam. Check addresses before the first send; the free email checker handles one at a time.

Short version

• Honest first: no fake "Re:", no invented familiarity, subject matches the body.
• Specific and short: their company, role or situation, important words first.
• Plain and lowercase-friendly: it should look like a message, not a campaign.
• Test on replies, with only the subject line changing.