Let’s open with some numbers pulled straight from the data:

We analyzed millions of cold email campaigns sent through lemlist and pulled out the exact copywriting tactics that move reply rates and booking rates. Below, I walk you through seven of them, step by step.

Cold email copywriting is crafting persuasive messages for leads or clients who have no prior relationship with you.

You have to grab attention and convince a stranger to act, whether that’s a reply, a booked call, or a purchase.

It’s harder than it sounds.

Unlike writing to a friend, coworker, or boss, cold email copywriting means building a genuine connection with a stranger in only a few words. And your email is one of dozens your prospect gets that day.

So you have to stand out and get your prospect to act, without coming off as gimmicky or sales-y.

It’s a fine line to walk.

That’s why we analyzed the data from millions of lemlist cold email campaigns, to find the statistics and insights that help you fine-tune your copywriting, get more replies, and book more meetings.

Let’s get started.

Here are the 7 best practices that help you write cold emails that convert.

Even the best-written cold email will fall flat if it’s sent to the wrong people.

In Cintell’s 2016 Understanding B2B Buyers benchmark study, 71% of companies that exceeded revenue and lead goals had documented buyer personas, compared to 26% of those that missed their targets.

Source: Cintell

Start your outreach with a specific buyer persona in mind, find contacts who match it, and you put yourself on the side of the teams hitting their goals.

So before you write a single line, define the audience you’re sending to.

How do you define that audience?

→ Make a list of your best clients

→ If you don’t have clients yet, list potential ones and start networking with them

→ Research the attributes of the clients on your list

→ Identify the attributes they share

→ Build a fictional profile of the person who would buy from each cluster of similar clients

→ In the profile, include their position, age, goals, path to purchase, and obstacles

→ Separate your personas into tiers, from most to least revenue

Once your personas are ready, prioritize tier-one. That focuses your effort on the clients most likely to bring in revenue fastest.

For a complete guide on identifying your target audience, use our guide on ICPs and buyer personas.

Once you have a targeted list, it’s time to write. The first thing your prospect sees is the subject line.

It’s one of the biggest factors in whether your email gets opened or ignored.

The first rule of subject lines: the shorter, the better.

When we analyzed millions of cold email campaigns, success rates dropped with every extra word added to the subject line.

So aim for 8 words or less. It helps prospects understand your message fast, and it won’t get cut off on mobile.

Other subject-line best practices:

→ Personalize with text variables like {{painPoint}} or {{Objective}}, or reference a detail specific to the prospect.

→ Ask a question, if it’s genuinely relevant to your prospect.

→ Add urgency by referencing an exclusive event or offer, when it’s real.

→ A/B test to find out what your audience responds to.

To learn more, plus 10+ subject lines with 80%+ open rates, read our data-based guide on B2B cold email subject lines.

Too many cold emails start with “Hi, my name is…” or “To introduce myself…”

Prospects care about one thing: how you help them hit their goals.

To measure this, we grouped emails by how often they talked about the prospect versus the sender. We counted how many times each email used “you,” “your,” “yours,” and so on.

Out of millions of cold emails, the ones that mentioned the prospect most got the highest average booking rates:

So what does that mean for your copywriting? Make the prospect the focus of every email, not you.

Here’s an example:

Gina opens with a long section about herself and her company. There’s no hook, and it isn’t clear what her connection to the prospect is.

Here’s the same outreach, this time focused on the prospect:

This version mentions the sender’s company once and spends the rest on the prospect’s company and needs. Gina shows she knows the prospect by congratulating her on a funding round, and she states clearly what the prospect gets: time saved by automating sales processes.

It’s tricky to pin down the right length. Long enough to get the details across, or short enough to read fast?

We tested it by analyzing the booking rate of thousands of cold emails. On average, emails around 120 words had the highest success.

That doesn’t mean you need exactly 120 words every time. Aim for 75-125 words: enough for the prospect to understand your message, without rambling.

And don’t neglect formatting. Those 120 words should be easy to scan, broken into short paragraphs of 1-2 sentences with line breaks between them.

Your prospect will only spend a few seconds on your email. Keep it short and easy to read.

For the full data on cold email length and formatting, read our guide on how long your cold emails should be.

When your emails are capped around 120 words, an image or two is a good way to get your message across without adding bulk.

When we analyzed reply rates of emails with and without images, adding 1 or 2 images boosted success:

But more than 2 images puts you at risk of lower reply rates, or a spam flag if the file size is too large. To go deeper on images and deliverability, read our data to know if images will land you in spam.

So when you add images, make sure they are:

→ no more than 2

→ tailored to your prospect

→ compressed

B2B cold outreach doesn’t have to be “boring to boring.” You can loosen up with casual language, and even emojis or exclamation points, if it fits your audience.

First, emojis. Should you use them?

When we analyzed average reply rates of emails with and without emojis, emails with emojis got 13% lower reply rates.

But that data set included emails with anywhere from 1 to 20+ emojis. If you include 1-2 emojis in an email targeted to an audience that uses them (influencers, freelancers, solopreneurs), you’re safe.

Exclamation points show a similar pattern:

Emails without exclamation marks got a slightly higher average reply rate than emails with them.

If your research shows your audience prefers formal language, skip the casual details. If you’re not sure, use this step-by-step guide on A/B testing to find the tone that works.

Personalization works. According to a Yes Lifecycle Marketing analysis of more than 7 billion emails, personalizing subject lines can increase open rates by up to 50%. The problem is doing it by hand. If you spend 10 minutes researching every prospect and drafting a custom opener, you burn hours before your first real conversation even starts.

AI changes the math. In ZoomInfo’s State of AI in Sales and Marketing 2025 survey, AI users report being 47% more productive and saving an average of 12 hours per week. Those hours go back to selling.

Inside lemlist, Smart Messaging handles the heavy lifting. It generates full outbound sequences, writes personalized intros and PS lines for each prospect, and uses AI Variables to clean and segment messy lead data so your copy actually fits the person reading it. You can even clone your voice from a single recording and send thousands of custom audio notes.

For bigger-picture planning, lemAgent acts as a conversational copilot. Describe your goal and ICP in plain language, and it builds a personalized multichannel campaign for you. It can also review past campaigns and suggest concrete message rewrites based on what performed.

Yes, AI can sometimes miss context a human would catch. But the goal here is augmentation, not replacement. Let AI handle the research, data work, and first-draft copy. You stay in control of final judgment and real conversations. That split is where the productivity gains compound.

You can generate your first campaign inside lemlist in minutes.

To recap, here are the best practices to optimize your cold email copywriting:

What is the ideal cold email length?
Around 120 words. In our analysis of lemlist campaigns, emails in the 75-125 word range earned the highest booking rates. Give the prospect enough to understand your message, then stop.

How long should a cold email subject line be?
Between 1 and 8 words. Success rates dropped with every extra word we added, and even 1-word subject lines performed well when they grabbed attention and signaled value.

Should you use images in cold emails?
Yes, in most cases. Adding 1 or 2 images raised reply rates in our data, and images alone don’t hurt deliverability. Keep them personalized, compressed, and no more than two per email.

How do you personalize cold emails at scale?
Use variables and AI instead of rewriting every email by hand. lemlist’s Smart Messaging generates personalized copy, cleans and segments lead data with AI Variables, and clones your voice for custom audio notes, so each message fits the person reading it.

Write every email for the prospect, not for yourself. Keep it short (around 120 words). Use your data and AI to personalize at scale, without burning hours on manual research.

Pick one tactic from this list and test it in your next campaign. If you want to put all seven to work in one place, grab our proven successful cold email templates and start your 14-day free trial to build your first sequence today (or book a demo if you’d rather see it live). lemlist is rated 4.7 out of 5 from 1,396 reviews on G2.