Cold Email Subject Lines: 60 B2B Examples and 9 Rules

Cold email subject lines have one job: get the right person to open the email, and set up a body that delivers on the promise. They do not have to be clever. The cold email subject lines that work best usually look like something a colleague would send: short, specific, and a little plain.

This guide gives you nine rules for writing subject lines, 60 examples sorted by the situation you are writing in, a list of lines to avoid, how preview text works as a second subject line, and how to test subject lines by replies instead of open rates.

What a cold email subject line has to do

A recipient decides what to do with a cold email in a couple of seconds, using three things: the sender name, the subject line, and the preview text (the first line of the body that many inboxes show next to the subject). The subject line has to do three jobs in that moment:

1. Look relevant to this person. A mention of their company, team, or a specific topic beats a general benefit.
2. Not look like marketing. Title case, exclamation points, and promises read like a newsletter, and newsletters get skimmed or filtered.
3. Match the email. An open that leads to a bait-and-switch earns an annoyed delete or a spam report, which is worse than no open.

9 rules for cold email subject lines

1. Keep it to two to five words. Many phones show only the first 30 to 40 characters of a subject. Short subjects also look more like internal email.
2. Use sentence case or lowercase. "question about your SDR hiring" looks typed by a person. "Question About Your SDR Hiring" looks like a campaign.
3. Be specific to them. Company names, team names, tools, events, and triggers make a subject relevant. "Quick question" is fine only when the preview text carries the specifics.
4. Never fake "Re:" or "Fwd:". Adding them to an email that is not a reply or forward is deceptive, and misleading subject lines are prohibited under the US CAN-SPAM Act.
5. Skip hype and pressure. No ALL CAPS, no "!!!", no "last chance", no "urgent". Invented urgency in a cold email reads as spam.
6. Promise only what the body delivers. If the subject says "idea for {{company}}", the first lines must contain the idea.
7. Use personalization fields carefully. A first name in the subject can work, but a broken field ("Hi {{first_name}}") or a wrong company name is fatal. Check that every field resolves before sending.
8. Ask real questions sparingly. A question can earn an open, but a vague "Are you free?" just creates suspicion.
9. Write the subject last. Once the body has a clear reason to write, the subject usually names that reason in a few words.

60 cold email subject lines by situation

Pick the group that matches why you are writing, then adapt the line. Replace every {{field}} with a real detail; if you cannot, pick a different line. These are first-email subject lines. For follow-ups in the same thread, keep the original subject.

Trigger events: hiring, funding, launches, expansion

1. {{company}}'s {{role}} hiring
2. {{number}} new {{team}} roles
3. after the {{round}} round
4. {{product}} launch
5. expanding to {{region}}
6. new {{team}} at {{company}}

A trigger subject tells the reader you noticed something real. It only works when the trigger and the body connect: the hiring push should lead to a problem new hires create.

Their content: posts, talks, podcasts, articles

7. your post on {{topic}}
8. your {{podcast}} interview
9. about your {{event}} talk
10. your take on {{topic}}
11. {{topic}}: one more angle
12. question about your {{article}}

Reference something specific from the content in the first line of the body. A subject that names their post followed by a generic pitch feels like a trick.

Referrals and mutual connections

13. {{mutual_name}} suggested I reach out
14. intro via {{mutual_name}}
15. {{mutual_name}} and {{topic}}
16. fellow {{community}} member
17. {{school}} alum with a question
18. we both know {{mutual_name}}

Only use these when they are true. A real referral is the strongest subject line there is; a fake one ends the conversation and damages your name.

Problem and question subject lines

19. question about {{process}}
20. {{process}} at {{company}}
21. how are you handling {{problem}}?
22. {{option A}} or {{option B}}?
23. who owns {{area}}?
24. {{metric}} after {{change}}

These work when you do not have a trigger and want the reader to self-qualify. The body should ask one question they can answer in a line.

Proof and peer subject lines

25. how {{similar_company}} fixed {{problem}}
26. {{similar_company}} and {{outcome}}
27. what {{peer type}} do about {{problem}}
28. {{outcome}} in {{timeframe}}
29. {{similar_company}}'s approach to {{process}}
30. a {{industry}} example

Name a customer only with permission, and only quote results you can back up.

Ideas and observations

31. idea for {{company}}
32. {{page or feature}} at {{company}}
33. 3 notes on your {{page}}
34. small fix for {{process}}
35. thought on {{initiative}}
36. noticed something on {{page}}

Observation subjects promise free work, so the body has to contain a real, specific idea, not a teaser for a call.

Resources and offers

37. {{topic}} checklist for {{role}}s
38. {{industry}} benchmark, if useful
39. teardown of {{process}}
40. template for {{task}}
41. {{topic}} notes from {{number}} teams
42. worth sending you this?

Ask before you send the resource. It keeps the first email link-free and turns interest into a reply.

Events and timing

43. {{event}} follow-up
44. before {{event}}
45. after your {{event}} session
46. {{event}} next week?
47. missed you at {{event}}
48. {{season}} planning for {{team}}

Event subjects work for a week or two after the event. After that, the shared context has faded.

Agencies and freelancers looking for new clients

49. idea for {{company}}'s {{channel}}
50. {{channel}} quick win for {{company}}
51. {{service}} for {{client type}}
52. 3 ideas for your {{channel}}
53. your {{channel}} vs {{peer}}'s
54. a {{channel}} audit, no strings

Service buyers want proof of skill. A subject that promises a specific idea, followed by that idea, does more than any list of services.

Job seekers, internships, and networking

55. {{role}} at {{company}}: a question
56. {{school}} student interested in {{team}}
57. internship question for {{team}}
58. advice on {{field}} at {{company}}
59. {{role}} applicant, referred by {{name}}
60. 15 minutes on {{topic}}?

The same rules apply outside sales: be specific, be honest about what you want, and make the ask small.

Cold email subject lines to avoid

Preview text: your second subject line

In many inboxes the first line of the body appears right after the subject. That line is effectively a second subject line, so do not waste it on "Hi Sam, hope you are well" or "My name is…".

Write the subject and the first line together:

• Subject: question about {{process}}
• First line: "Saw {{company}} is hiring three SDRs, so I am guessing {{process}} is about to get busier."

The subject earns the glance, and the first line gives the reason to keep reading. When the subject is short and plain, the preview text should carry the specifics.

Follow-up subject lines: same thread or new?

Follow-ups usually stay in the same thread, so the subject becomes "Re: {{original subject}}". That is honest, because it really is a reply to your earlier email, and it lets the reader see the history.

Start a new thread with a new subject only when the angle is new, such as a fresh trigger or a different person at the account. The cold email follow-up guide covers when to switch, the day 3, 7, 14 schedule, and eight follow-up templates.

How to test cold email subject lines

Open rates are a weak signal for cold email. Apple Mail Privacy Protection and some security scanners load tracking images automatically, so many "opens" are not people. Judge subject lines by what happens after the open:

• Positive reply rate (interested or referral replies divided by delivered emails) is the number that matters.
• Negative signals such as opt-outs and spam complaints show when a subject overpromises.
• Test one variable at a time. Keep the body and audience the same and change only the subject.
• Give each version enough volume. A few hundred delivered emails per version is a reasonable floor before deciding; ten replies versus eight is noise.

The outbound experiment design guide explains how to structure these tests so you do not fool yourself.

Writing subject lines in Reach Agents

A Reach Agents email campaign is a first email plus up to four follow-ups. You write the subject line and messages yourself, or let AI write them from each lead's context and the evidence that put them on the list. You preview the sequence before launch, so you can check that personalization fields resolve for each lead.

Follow-ups stop automatically when a lead replies or opts out. Email goes out as plain text from your own SMTP/IMAP mailboxes or from domains and mailboxes bought in the app, with warmup and address verification. Replies land in one unified Inbox alongside LinkedIn, X, Telegram, WhatsApp, and Instagram conversations.

Need the email body too? The cold email templates guide has twelve first emails by situation, each with a matching subject line.

Frequently asked questions

How long should a cold email subject line be?

Two to five words is a good range, and under about 40 characters keeps it readable on most phones. Short subjects also look more like email from a colleague than from a marketing tool.

Should I put the recipient's name in the subject line?

You can, but company names, team names, and specific triggers are usually more useful than a first name. If you use any personalization field, check that it resolves for every lead, because a broken field is worse than none.

Are lowercase subject lines better for cold email?

Lowercase or sentence case looks more personal than title case, which reads like a campaign. Either is fine; what matters more is that the subject is specific and honest.

Can I use "Re:" in a cold email subject line?

Only when the email really is a reply in an existing thread. Adding "Re:" or "Fwd:" to a first email is deceptive, and misleading subject lines are prohibited under the US CAN-SPAM Act.

How much does Reach Agents cost, and is there a free trial?

Social accounts such as LinkedIn and X are $49 per connected account per month. Email is priced by your sending setup, so talk with us about mailboxes and volume; the details are on the pricing page. The 7-day free trial includes 2 accounts and $15 in credits, and no card is needed to start.

Start your 7-day free trial at app.reachagents.ai, write a subject line that names your real reason for writing, and preview every email before it sends.