Every guide to cold email is a list of writing tips, and every list is roughly the same list. Keep it short. Ask a question. Use their name. Almost none of those cold email guides says how much any tip is worth. Two of the numbers those guides are built on stopped being true years ago.
This page puts a measured number on each common cold email tip, so you can see which advice holds up. It covers what to write in a cold email. Whether a cold email reaches the inbox at all is a separate job, covered in how to stop your emails going to spam.
A cold email reply rate of 8.5% beats every other cold channel
The largest published count of cold email replies comes from the SEO blog Backlinko and the outreach platform Pitchbox.
- Of 12 million outreach emails sent, 8.5% got a reply back from the person who received it.
- A cold email is answered roughly 100 times more often than a display ad is clicked.
- Backlinko's 8.5% reply rate is the high end for cold email, not the average. Two counts of cold sales emails put the reply rate at 2.09% and 3.43%.
- Backlinko's study of 12 million emails publishes no method, so it is the biggest count of cold email replies rather than strong evidence.
| How you reached the person | How often they respond | How good the evidence is |
|---|---|---|
| A LinkedIn message | 18% to 25%, claimed | Vendor claims with no stated method |
| An email to a colleague who knows you | 13.58% | My own test on 35,480 emails |
| A cold email to a blogger or journalist | 8.5% | 12 million emails, method not published |
| A posted letter to a bought list | 2.0% to 4.4% | Industry survey, seen through other sites |
| A cold email selling something | 2.09% to 3.43% | 2 million and 20 million emails |
| A display ad, averaged across every type | 0.46% click | Ad platform reporting |
| A display ad on the open web | 0.05% to 0.08% click | Ad platform reporting |
Nearly half of cold email replies are out of office notes
An 8.5% reply rate is good for cold email, but a reply does not mean the person who sent it is interested.
- A study of more than 2 million cold emails across 161 campaigns sorted its 61,770 replies into what they actually said.
- In that study of 2 million cold emails, 45.1% of replies were automatic out of office notes.
- In the 2 million cold email study, 29.9% of replies were refusals from people who were not interested.
- In the 2 million cold email study, only 14.1% of replies came from someone who was actually interested.
- If 14.1% of replies are interested, Backlinko's 8.5% reply rate means only about 1.2% of cold emails produce a real lead.
Sending a second email beats writing a better first one
The strongest evidence on following up versus rewriting comes from two United States government teams that test the wording of official messages and kept every result.
- The economists Stefano DellaVigna and Elizabeth Linos collected all 126 randomised trials run by two US government message-testing teams, covering more than 23 million people. 87% of those 126 trial results had never been published, so the trials that failed were counted too.
- In the 126 government trials, reminders and prompts to make a plan raised the share of people who acted by 2.54 percentage points, the largest effect of any approach tested.
- In the 126 government trials, making the message simpler and clearer raised the share of people who acted by 1.19 percentage points, less than half the effect of a reminder.
- Backlinko's study of 12 million outreach emails also favours follow-ups, with one follow-up email raising replies by 65.8%.
- Those 126 government trials were about paying fines and claiming benefits, so reminders beating rewrites should carry over to cold email, but the exact numbers will not.
Use Camera to Clipboard to give your follow-up something new to say
The hard part of a follow-up email is having anything new to add, and a photograph is the cheapest new thing to add. Camera to Clipboard, one of my own apps, takes a picture on your phone and puts it straight onto your computer's clipboard.
- A follow-up that only says you are checking in gives the reader nothing to answer.
- A photo of the thing you are writing about turns a follow-up email into a second reason to reply.
- A photo taken with Camera to Clipboard arrives on your computer the moment you take it, with no detour through email or a cable.
Putting the reader's name in a subject line lifted opens 20%
Every cold email guide says putting the reader's first name in the subject line no longer works. The one randomised test of names in subject lines found the opposite.
- Navdeep Sahni, Christian Wheeler and Pradeep Chintagunta, three marketing researchers, ran randomised subject line experiments with three organisations, sending to millions of people. Their subject line study was published in the journal Marketing Science in 2018.
- Adding the recipient's own name to the subject line raised opens from 9.05% to 10.80%, a lift of 20%. The 20% lift in opens was measured before Apple's Mail app made open rates unreliable.
- With the recipient's name in the subject line, sales enquiries rose 31%, from 0.39% to 0.51% of everyone emailed.
- With the recipient's name in the subject line, the share of people unsubscribing fell 17%, from 1.2% to 1.0% of everyone emailed.
- The popular claim that deeply personalised cold emails get a 17% reply rate, against 7% for basic templates, has no experiment behind it anywhere.
Emails of 50 to 125 words got the most replies
The rule to keep an email to 50 to 125 words comes from one source, a 2016 analysis of more than 5.3 million messages by Boomerang, an email plugin.
- In Boomerang's 5.3 million messages, emails of 50 to 125 words got a reply more than half the time.
- In Boomerang's data, emails under 50 words got a reply 44% of the time, the same rate as emails of 500 words.
- In Boomerang's data, emails longer than 2,000 words got a reply less than 35% of the time.
- Boomerang is a plugin for chasing your own sent mail, so its 5.3 million messages are mostly email between people who know each other.
Use Repeat Recorder to practise the call your email asks for
A cold email is only trying to start a conversation, and that conversation decides whether you get what you asked for. Repeat Recorder, one of my own apps, plays your own voice back to you so you hear yourself before the person you are calling does.
- Repeat Recorder plays your recording back about a second after you stop speaking.
- Repeat Recorder's automatic mode starts recording when you speak and replays when you stop, without you touching the screen. Hands-free recording makes Repeat Recorder usable while driving or walking.
- You can save the Repeat Recorder recordings worth keeping into folders you name yourself and replay any of them on a loop.
Replies kept rising past 125 words and only fell past 500
The 5.3 million Boomerang messages are private, so I ran the same length and question tests on a public set of company emails anyone can download.
- The Enron collection is a public set of real company email, released by a US federal investigation in 2003. Of the 35,480 Enron emails with a readable body that I used, 13.58% got a reply.
- In the Enron emails, 16.90% of emails of 50 to 125 words got a reply, against 12.40% of emails under 50 words.
- In the Enron emails, 19.31% of emails of 126 to 500 words got a reply, beating the recommended 50 to 125 words at 16.90%. Enron emails longer than 500 words got a reply 13.24% of the time, the first length where replies fell.
- In the Enron emails, 16.89% of emails sent to more than one person got a reply, against 11.93% of emails sent to one person.
Asking a question in the email nearly doubled the reply rate
I counted questions in the subject line and in the email text separately, in the 35,480 Enron emails.
- Enron emails that asked one to three questions got a reply 21.22% of the time, against 11.40% for Enron emails that asked nothing. Asking four or more questions in an email did not raise replies any further.
- Emails that asked a question got more replies at every email length, so the question effect is not just short emails asking more.
- A question mark in the subject line, with no question in the email itself, did nothing at all.
- Ending with a line like "looking forward to hearing your thoughts" does not count as asking anything.
- The question figures are a pattern, not proof, because somebody with a real question to ask is in a different situation from somebody sending an update.
Use Camera to Clipboard to put real proof in a cold email
The randomised subject line test showed that the reader's name buys attention, and a photograph in the email catches attention too. Camera to Clipboard, another of my own apps, puts a phone photo straight onto your computer's clipboard.
- A photo taken with Camera to Clipboard arrives on your computer's clipboard the moment you take it, with no cable and no upload. To set up Camera to Clipboard, you pair the phone and the computer once by scanning a code on screen.
- A photograph of the thing you are writing about proves to the reader that the cold email is not a template.
- Camera to Clipboard works for anything physical that would otherwise need a scanner.
Writing at third grade level beat college level by 36%
Boomerang's 5.3 million messages were also scored for reading difficulty.
- In Boomerang's data, messages written at a third grade reading level got a reply 53% of the time, against 39% for messages at college level.
- A third grade reading level means short sentences and common words, not a childish tone.
- In my own test on the Enron emails, 14.93% of emails below a grade 7 reading level got a reply, against 11.96% of emails at college level and above. In the Enron emails, simpler writing got 25% more replies than college level writing, not the 36% Boomerang found.
- In the Enron emails, writing at a grade 4 to 6 reading level got more replies than anything simpler.
- The reading level reply figures are a pattern across many emails, not proof that simplifying your own draft will raise your replies.
Give a stranger a longer subject line than someone who knows you
The two biggest counts of email replies, by Boomerang and Backlinko, disagree about subject line length because Backlinko measured emails to strangers and Boomerang measured emails mostly between colleagues.
- Boomerang found 3 to 4 word subject lines drew the most replies across 5.3 million messages, mostly between people who know each other.
- Backlinko found 36 to 50 character subject lines did best across 12 million cold outreach emails to strangers.
- Use about 6 to 8 words when writing to a stranger and about 4 when writing to someone who knows you. A stranger needs to be told who you are and why you are writing.
- In my own test on emails between colleagues at Enron, subject lines of 1 to 4 words got a reply 13.98% of the time, against 12.29% for subject lines of 5 or more words.
- The specific advice to use a 3 to 4 word subject line has nothing behind it, because 1 to 2 word subject lines did just as well in the Enron emails.
Every cold email rule ranked by the evidence behind it
Each common cold email rule below is shown with the evidence behind it and how much it is worth, which most cold email guides leave out.
| The rule | How good the evidence is | How much it is worth | What happened when I retested it |
|---|---|---|---|
| Send a follow-up | 126 randomised trials, 23 million people | 2.54 points, the largest of any approach | Not retested, my data cannot tell a follow-up from a first email |
| Put the person's name in the subject line | Randomised experiment, millions of emails | 20% more opens and 31% more enquiries | Not retested, opens are not visible in my data |
| Ask one to three questions in the email text | 5.3 million messages, no experiment | 86% more replies in my own test | Confirmed, and larger than the original claim |
| Email more than one person | 12 million outreach emails, no experiment | 42% more replies in my own test | Confirmed independently |
| Keep the email to 50 to 125 words | 5.3 million messages, no experiment | Writing over 50 words won 36% more replies | Failed, 126 to 500 words did better still |
| Write at a third grade reading level | 5.3 million messages, no experiment | 25% more replies in my own test | Partly, grade 4 to 6 beat anything simpler |
| Use a 3 to 4 word subject line | 5.3 million messages, no experiment | No better than a 1 to 2 word subject line | Failed, the specific number does nothing |
| Send it on a Wednesday | One count of emails, no experiment | 2 points over the worst day of the week | Not retested, send days are not comparable |
| Research each person deeply instead of using their name | Vendor claims with no stated method | Never measured against a control group | Not retested, my data has no cold approaches |
Use Repeat Recorder to read your cold email out loud
Two cold email rules, the reading level rule and the length rule, are about how the writing sounds, which is hard to judge by eye. Repeat Recorder, one of my own apps, plays your voice back a second after you stop speaking.
- A sentence you run out of breath reading aloud is too long for a third grade reading level.
- Reading a draft aloud takes about 25 seconds at the 50 to 125 word length that got the most replies. If reading your draft aloud takes a minute, it is roughly double the 50 to 125 word length.
- You can set Repeat Recorder to record hands free and loop the playback as many times as you want.
Ten cold email openings rewritten to ask something
Each rewritten cold email below gives a subject line and the one question the email exists to ask.
| Who you are emailing | What the usual version breaks | The subject line most people send | The subject line and the question to replace it |
|---|---|---|---|
| A blogger you want to be mentioned by | Asks nothing at all | Quick question | Your Perth cycling routes guide. Is the new Kwinana path worth adding to it? |
| A podcast host you want to be a guest of | Asks nothing at all | Podcast guest | Guest idea on what small apps charge. Would that fit your run of solo founders? |
| A professor you want to research with | Asks nothing at all | Research opportunity | Your 2025 paper on tidal sediment. Are you taking students this year? |
| Someone who ignored your first email | Never gets sent at all | Nothing, because most people never follow up | Following up on the Kwinana path. Still worth sending you the photo? |
| A journalist who covers your industry | Subject line means nothing to a stranger | Story idea | Figures on WA rental listings you may want. Do you cover the quarterly numbers? |
| A hiring manager with no job advertised | Subject line means nothing to a stranger | Application | Your team's Android rewrite. Are you hiring for it yet? |
| A supplier you want a price from | Subject line means nothing to a stranger | Enquiry | 500 sheets of your 3mm marine ply. Can you quote for August delivery? |
| A person you met once at an event | Subject line names nothing specific | Great to meet you | The Fremantle meetup and your caching problem. Did the second approach work? |
| A customer at a company you researched | Subject line is far too long | Helping your company streamline operational efficiency and reduce overheads | Your three Perth warehouses. Who counts the stock in them now? |
| A conference organiser | Subject line is far too long | Speaking proposal submission for your upcoming annual developer conference | Talk idea on apps that work offline. Is that track still open? |
Conclusion: how to write a cold email that gets replies
These cold email rules are ordered by how much each one is worth, largest first.
- Make sure the email arrives before you rewrite it. One in six emails never arrives.
- Send a follow-up email. A follow-up beat every rewrite it was ever tested against.
- Ask one clear question in the email itself. Asking a question nearly doubled replies in my own test.
- Email more than one person at the organisation. Emailing more than one person got 42% more replies.
- Put their name or their own specific thing in the subject line. The reader's name in the subject line got 20% more opens.
- Write a cold email of between 50 and 500 words. An email that is too short loses far more replies than one that is too long.
- Use short sentences and common words. Short sentences and common words got 25% more replies.
- Give a stranger 6 to 8 subject line words, and someone who knows you 4. A stranger needs to be told who you are.
- Count the replies from interested people, not every reply. Nearly half of all cold email replies are automatic out of office notes.