The science of B2B cold email subjects that convert (+ examples)

June 20, 2023

If your B2B cold email subject lines don’t hook your prospects, they won’t read your emails.

So we analyzed the subject lines from millions of cold outreach campaigns to find out what works, and what doesn’t.

In this article, you’ll learn 6 proven tactics of cold email subject lines with > 80% open rates, plus a list of high-conversion subject lines from real campaigns.

6 tips to write a B2B cold email subject line

Instead of sifting through hundreds of subject line examples, learn how to write yours from scratch.

You’ll be able to better target it to your prospects and consistently hit your goal of higher open rates.

So here are 6 tips to write B2B cold email subject lines that convert, based on a real study of successful campaigns.

Tip 1:  Keep your subject short and sweet

Your email subject line should be between 1-8 words. (Yes, even 1-word subject lines are successful!)

It needs to grab attention and communicate value without taking up a lot of space. Readers should click after 1 look.

In fact, we found that open and reply rates decrease on average with every extra word you add to a subject line:

A bar graph with the text "How many words should you put in your cold email subject line?" The first bar, for 1-2 words, shows the highest reply rates. with 25% lower rates are subject lines from 3-8 words, 20% lower for subjects with 9-13 words, and very low reply rates for email subject lines with 13+ words

Why is this?

Your email is fighting for attention in the recipients’ cluttered inboxes.

To catch the decision-makers, grab them right away - or else your message will be forgotten.

Your subject line should also be short enough to appear in full on mobile. A subject line that looks like this on the recipient's desktop:

An email subject line on a browser window that shows the entire subject line: "saying no to $30,000,000 from investors?"

…will be cut short on a phone screen. 👇

A screenshot of an email on mobile. The subject line is cut short and shows "Saying no to $30,000,000 from invest..."

Make your subject lines 8 words or less, and put the most powerful words at the beginning.

Tip 2: Write personalized subject lines

Talk directly to your prospects, and make it personal.

But don’t be lazy about it.

Simply adding “you” or {{firstname}} as your only personalization tactic won’t make your prospects open your emails.

To test this, we analyzed hundreds of thousands of lemlist campaigns, and just having “you” or {{firstname}} in the subject line didn’t make a notable difference:

A bar graph with the title "'You' or {{firstName}} in the subject line won't raise open rates" The bars show an even open rate for subject lines with 'you', without 'you', with {{firstname}}, and without {{firstname}}

So what does that mean?

You’ll have to take your personalization a step further than adding basic keywords.

Here are two ways that you can do that.

  1. Try more specific variables than just {{firstname}}.

    Personalize your subject lines with custom variables like {{painPoint}}, {{competitor}}, {{commonGround}}, or {{Objective}}.

    With tools like lemlist, you can automatically personalize your subject lines and messages. If you don’t have an account yet, sign up here for free.
  2. Reach out according to a specific trigger. Mention a piece of content or project the lead just shared, or address a need they have at this exact moment.

    For example: “Thoughts on your last video” or “Congrats on XYZ!”

Tip 3: Ask a question - if it’s relevant

You might have heard that asking a question is the best way to engage with a prospect. The strategy is to provoke a response and make leads open the email.

So, are questions a proven way to get people to open an email? According to the data, not necessarily.

Adding a question to your B2B cold email subject won’t guarantee success. And if you try to over-optimize by adding multiple question marks, this will hurt your open rate.

A bar graph with the title "should you ask a question in your subject line? Not necessarily." The bars show even open rates around 35% for subject lines that are questions and subject lines that aren't questions

So how should you use questions in subject lines?

The solution is to better use questions in cold email subject lines:

  1. Be specific - ask a question that addresses the prospect’s specific pain point. (e.g. “Need help with {{painpoint}}?”)
  2. Challenge their expectations - provoke a response by surprising them (e.g. “Happy with 50% open rates?”)

Tip 4: Keep your subject line casual

B2B cold email subject lines don’t need to be overly formal.

People skim their inboxes before deciding what email to open. Make your subject line simple and clear, so that the reader understands immediately what you’re sending.

In our analysis of cold outreach campaigns, high readability alone had the power to increase open rates by 6%.

So write your subject lines in simple terms that a kid would understand. You can use an app like Hemingway to check the complexity of your writing.

Tip 5: Add urgency

Your prospect should have a sense that they need to act on your message now- instead of letting it get lost in minutes. The action they’re taking should be clear and easy to follow.

And don’t fake it. Using all caps, too many emojis, or exclamation points doesn’t lead to higher open rates - and using too many of them can get you marked as spam. 👇

A line graph with the title "Should you use exclamation points in your cold email subject line?" The line shows the highest open rates with subject lines that have 0-1 exclamation points, then decreases with the more exclamation points that are added to the subject

How can you add urgency and emotion without being spammy?

Make an exclusive offer (e.g. “an exclusive gift for you, {{firstname}}) or add a fear of missing out (e.g. “Here’s an invite to the event of the year, {{firstname}}).

Just make sure it’s tailored to your prospects.

Tip 6: A/B test your cold email subject lines

Of course, the best way to learn what works in your cold outreach is to gather your own data.

Try two variations of the same subject line. For example: subject lines with or without emojis.

Send one variation to 50% of your audience, and the second variation to the other 50%.

Make sure that there are enough people in the email list for the results to be relevant. Aim for 100-200 people.

Once that’s done, you can compare the open rates, clicks, and replies for each subject line. You’ll learn which techniques your audience responds best to.

An example of A/B testing subject lines: the first says "An exclusive invite for [firstName]! with a label that says "adds exclusivity by making it seem like they need an invite." The second subject line says "Join us at the biggest event of 2023, [firstName]!" with an arrow that says "plays with the fear of missing out with words like "us" and "biggest."

10 B2B cold email subject lines that convert (based on data!)

These subject lines all got 80%+ open rates and were sent at least 50 times.

We’ll break down why they were so successful, and how you can turn them into many variations that get the same results.

Subject line 1: Loved your last article!

Why this subject line works
: it’s short, simple, and personal. The email was sent within days of the prospect’s published content that aligned with the sender’s value proposition.

It focuses on the prospect, and it’s personal without overusing personalization buzzwords.

How you can use it: Reach out to your prospects based on specific timing triggers.

Congratulate them on recent work or achievements, instead of selling your product immediately. This is also a great subject line for networking.

Subject line 2: Last call {{firstname}}… closing soon 🔒

Why this subject line works
: it adds urgency and intrigue. This example came from a follow-up email, so the lead already had context for the offer that was ending.

With this subject line, the lead is incentivized to act quickly, open the email, and respond.

How you can use it: A subject line like this is best used as a second or third contact, once the lead already has an idea of the value you’re offering.  Use it as a push to get them to act in a short timeframe, once you’ve already warmed them up.

Subject line 3: little surprise for you {{firstName}}!

Why this subject line works:
it’s expressive, sparks curiosity, and offers something to the prospect in a friendly and casual way.

How you can use it: Use a subject line like this when you are sure to add value in your message. Match it with a helpful resource, a referral, or a free trial that addresses your prospect’s specific needs.

Subject line 4: Collaboration with - {{Domain}}

Why this subject line works:
it’s short, simple, and to the point. The prospect knows exactly what is being offered, and how they can act on it.

How you can use it: Use a subject line like this when your prospect is already familiar with your domain or brand name. Include social proof in your message. Otherwise the offer of a collaboration will not be enough of a hook.

You can do this by connecting via LinkedIn first, or if you have already interacted with this prospect online or in person.

Subject line 5: {{firstName}} how about we have a chat?

Why this subject line works
: it’s casual and friendly. It doesn’t ask too much from the prospect and presents a clear action: just a quick chat.

How you can use it: Pair this subject line with an email that offers a clear benefit to the prospect. Deliver value immediately, so that your prospect is incentivized to take time out of their schedule for a call with you.

Subject line 6: # ideas for {{painPoint}}

Why this subject line works:
it addresses the prospect’s pain point and offers actionable solutions.

How you can use it: This one calls for in-depth research up front in order to understand the different pain points. The {{painPoint}} should be narrow and specific to your prospect.

Subject line 7: Question about company culture @ {{companyname}}

Why this subject line works
: it sparks the prospect’s interest without selling anything. This subject line was used by an HR SAAS company, so the company culture topic transitioned easily into their core offering.

How you can use it: Swap out “company culture” for a detail that is more specific to your prospect and product.

Make your question the first line, or hook, of your email. Your prospect should see the subject and first line in the preview and know immediately what you are asking.

Subject line 8: Ideas & feedback for you & {{companyname}}

Why this subject line works:
Companies are always looking for customer feedback to make their products and service better. This offers some genuine user feedback, which the sender transitioned into a discussion of how they could help with the company’s specific needs.

How you can use it: Give the business legitimate and actionable feedback in your message. Add details that are relevant to them. Again, do some research ahead of time.

Subject line 9: Hey {{firstName}}, congrats on your funding round

Why this subject line works
: it is timely and specific. This was sent by a salesperson offering a product for sales teams, so the funding round meant resources for the startup to scale their team.

How you can use it: Find a specific trigger that relates to your product (funding round, just started a new job, IPO, etc.) and congratulate your prospect. Then offer a resource, call, or idea that is valuable to them in this specific moment.

Subject line 10: Build {{companyName}} like {{commonInterest}}

Why this subject line works
: it’s targeted and builds FOMO. You already know the prospect is interested in {{commoninterest}}, and they don’t want to miss out on building their business.

How you can use it: You’ll need to find a common interest between yourself and your prospect. It could be an entrepreneur, mutual connection, or even a sports team, as long as it’s relevant and sparks their interest.

Cold email subject lines to avoid

Finally, here are the cold email subject lines that had the lowest success rate of our analysis.

As you write your subject line, use these examples to know what NOT to do.

  • ❌ Your Video Will Be Deleted In 3 Days! - spammy, gimmicky, cheap. Don’t chase useless clicks. Next!
  • {{firstName}} 🤩 Special 25% OFF Coupon - sounds like a scam, and not specific enough. 25% off what - and why is it helpful to your prospect? What is your request?
  • Launching your own NFT marketplace has never been easier - too long, not specific enough. Why would this prospect want an NFT marketplace? How is it easier?
  • 90% of companies are struggling with hiring developers. See why. - too long, reads like the title of a listicle instead of a helpful email.
  • Act now {{firstname}}, this offer will expire! - gimmicky and includes trigger words like “act now” that can get your email marked as spam.

To make sure you’re not writing spammy subject lines, here is a list of 20 spam trigger words to avoid:

A chart of spam words that can get your email marked as spam. The words are "Congratulations! 100% Free No fees Win - Click now Make money LIMITED TIME! Act now Call now You’re a winner Not spam Get paid 12. No cost 13. Work from home 14. Get started free 15. Increase sales 16. About to expire 17. Unlimited 18. Join millions 19. Satisfaction guaranteed 20. Claim"

Key takeaways

Great B2B cold email subject lines are what drive your prospects to open and act on your messages.

So when your emails get opened, that leads to more meetings, more sales, and more revenue. You hit your goals faster.

To write subject lines that convert:

✔️ Make them personal

✔️ Make them timely

✔️ Make them short

…And don’t rely on gimmicks or impersonal “hacks.”

P.S. If you want useful templates and text variables to personalize your campaigns, try lemlist. You can sign up for free here - no card required!

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