Cold email best practices: 11 rules from 1,161,237 emails we sent
These cold email best practices held in 1,161,237 first emails Sales.co sent from Oct 6, 2025 to Oct 25, 2026. Offer to send something instead of asking for a call (0.77% vs 0.53% human replies per email, across 555,762 and 157,733 emails). Put their first name in the subject and keep it to 5 to 7 words. Greet them by name, and write one or two paragraphs with one question. Each of these 11 rules got at least 10% more human replies than breaking it, and kept that lead with our largest sender removed. The 3 subject line rules come from 954,794 first emails in the same window.
By Ryan Doyle, co-founder of Sales.co · Updated November 9, 2026 · Data through October 25, 2026
1,161,237
first emails, Oct 6, 2025 to Oct 25, 2026
8,168
human replies, 0.70% of emails
58
sending workspaces; the largest sent 16% of emails
Each rule, with the numbers
Black bar: emails that followed the rule. Grey bar: emails that broke it. Every rule was checked again with our largest sender removed.
01
Offer to send something. Don't ask for a call.
End on an offer: a short video, an example, a list. Of the 4 endings we measured, asking for a call got the fewest human replies and the fewest interested replies.
DoWant me to send over the 2-minute walkthrough?
Don'tDo you have time for a quick call this week?
+46%
human replies per email
Offers to send something0.77%
Asks for a call0.53%
- Largest sender removed
- +37%
- Human replies counted
- 4,264 vs 828
- Interested replies
- 0.25% vs 0.10% (1,370 vs 159)
- Emails compared
- 555,762 vs 157,733
02
Put their first name in the subject.
A subject with their name in it reads like it was written to one person, because it was.
DoSarah, idea for Acme's evening calls
Don'tIdea for Acme's evening calls
+55%
human replies per email
First name in subject0.90%
No first name0.58%
- Largest sender removed
- +40%
- Human replies counted
- 3,060 vs 3,304
- Interested replies
- 0.31% vs 0.19% (1,065 vs 1,101)
- Emails compared
- 340,650 vs 570,399
03
Write a 5 to 7 word subject.
One and two word subjects were the worst length we sent. A subject long enough to say what the email is about did best.
DoSarah, idea for Acme's evening calls
Don'tQuick question
+71%
human replies per email
5-7 words0.83%
1-2 words0.48%
- Largest sender removed
- +68%
- Human replies counted
- 327 vs 435
- Interested replies
- 0.39% vs 0.16% (155 vs 146)
- Emails compared
- 39,483 vs 89,691
04
Capitalize the first letter of the subject.
The all-lowercase subject is a known cold email trick, and it got fewer replies than a normal sentence.
DoQuick idea for Acme
Don'tquick idea for acme
+34%
human replies per email
First letter capitalized0.72%
All lowercase0.54%
- Largest sender removed
- +18%
- Human replies counted
- 3,497 vs 279
- Interested replies
- 0.22% vs 0.15% (1,074 vs 76)
- Emails compared
- 488,502 vs 52,097
05
Greet them by first name.
"Hi there," reads like a list. "Hi Sarah," reads like one person wrote to another.
DoHi Sarah,
Don'tHi there,
+47%
human replies per email
"Hi Sarah,"0.81%
Greeting without a name0.55%
- Largest sender removed
- +39%
- Human replies counted
- 5,208 vs 2,384
- Interested replies
- 0.26% vs 0.13% (1,637 vs 555)
- Emails compared
- 641,830 vs 433,777
06
Say who you are and what you do.
We counted pronouns. Emails that used "I" and "we" more than "you" got more replies than emails built around "you". In practice that means saying who is writing and what you do.
DoI'm Ryan from Fieldline. We schedule service techs for HVAC companies.
Don'tYou're probably losing jobs after 5pm, and your team...
+15%
human replies per email
More "I/we" than "you"0.75%
More "you" than "I/we"0.65%
- Largest sender removed
- +22%
- Human replies counted
- 3,985 vs 2,729
- Interested replies
- 0.23% vs 0.17% (1,209 vs 723)
- Emails compared
- 531,762 vs 420,521
07
Keep it to one or two paragraphs.
Word count made no clear difference once the largest sender was removed. The number of paragraphs the reader has to get through did.
DoTwo short paragraphs and a sign-off.
Don'tSeven one-line paragraphs stacked down the screen.
+45%
human replies per email
1-2 paragraphs0.84%
7 or more0.58%
- Largest sender removed
- +18%
- Human replies counted
- 490 vs 136
- Interested replies
- 0.26% vs 0.13% (153 vs 31)
- Emails compared
- 58,122 vs 23,465
08
Ask exactly one question.
An email with nothing to answer got the fewest replies. Two or more questions made no clear difference against one.
DoWant me to send it?
Don'tLet me know if this is of interest.
+29%
human replies per email
One question0.71%
No question0.55%
- Largest sender removed
- +21%
- Human replies counted
- 5,955 vs 437
- Interested replies
- 0.21% vs 0.13% (1,761 vs 100)
- Emails compared
- 841,986 vs 79,657
09
Leave out the stats.
Emails with a "40% more pipeline" or "3x faster" claim got fewer replies, and the gap in interested replies was wider.
DoTwo HVAC shops your size use it for evening calls.
Don'tOur clients book 3x more jobs.
+12%
human replies per email
No % or Nx figure0.72%
A % or Nx figure0.64%
- Largest sender removed
- +19%
- Human replies counted
- 6,530 vs 1,638
- Interested replies
- 0.21% vs 0.16% (1,952 vs 402)
- Emails compared
- 906,894 vs 254,343
10
Cut the exclamation marks.
Excitement from a stranger reads as a sales pitch.
DoCongrats on the new Tampa location.
Don'tCongrats on the new Tampa location!
+31%
human replies per email
No exclamation mark0.71%
One or more0.54%
- Largest sender removed
- +17%
- Human replies counted
- 7,977 vs 191
- Interested replies
- 0.21% vs 0.10% (2,320 vs 34)
- Emails compared
- 1,126,029 vs 35,208
11
Add a P.S.
The P.S. is the line people read after skimming the rest. Use it for something true and personal that asks for nothing.
DoP.S. Saw the new Tampa location. Congrats.
Don't(nothing after the sign-off)
+29%
human replies per email
Has a P.S.0.89%
No P.S.0.69%
- Largest sender removed
- +23%
- Human replies counted
- 724 vs 7,444
- Interested replies
- 0.28% vs 0.20% (231 vs 2,123)
- Emails compared
- 81,275 vs 1,079,962
An email that follows all 11
Written for this page, for a made-up HVAC scheduling company.
Subject: Sarah, idea for Acme's evening calls
Hi Sarah,
I'm Ryan from Fieldline. We schedule service techs for HVAC companies, and I noticed Acme's booking line closes at 5pm.
I put together a one-page breakdown of how two shops your size book evening calls without hiring. Want me to send it?
Ryan
P.S. Saw the new Tampa location. Congrats.
Advice that made no clear difference
Common cold email rules that didn't move replies by 10% both overall and with the largest sender removed. Shown as overall / largest sender removed.
- Keep it to 25-50 words+19% / +0%
- Write at a 4th-5th grade reading level+8% / -32%
- One sentence per paragraph-6% / +4%
- Tell a customer story+2% / +2%
- Mention their company+8% / +8%
- Cut "hope you're well"-6% / +2%
- Avoid hedge words (might, maybe)-3% / -12%
- Write in an informal tone+23% / +8%
- Ask a question in the subject+4% / -7%
- Put a number in the subject+1% / +7%
Limits and the strongest objection
This is observational data, so it shows which emails got more replies and does not prove the trait caused them. Different senders write different emails to different lists, so a trait can look good because the senders who use it have better lists. Two checks limit that: every rule is checked again with the largest sender removed (it sent 16% of the emails), and no group is shown when one sender made more than 45% of it.
The rules also overlap. An email that follows one often follows others, so the gaps don't add up, and part of each gap may belong to the rest. These are Sales.co's own campaigns, with our clients' lists and offers; a different mix of industries and offers may show different gaps. Treat each rule as a strong bet for your own split test.
For reply rates across all our sends, see the cold email statistics, and for when to send, the best time to send cold email. To check a subject line against these rules, use the subject line grader; to check a draft for spam trigger words, the email spam checker.
Method and FAQ
Cite as: Sales.co, "Cold email best practices: 11 rules from 1,161,237 emails we sent", https://sales.co/research/cold-email-best-practices, data through October 25, 2026.
How the data was collected
- Source: the text of every cold email Sales.co sent from October 6, 2025 to October 25, 2026 (1,283,765 first emails scanned), and the replies the sending tool labeled.
- Unit: recipient thread: one recipient address in one sending workspace, described by the first email that address got. 1,161,237 recipient threads from 58 sending workspaces. Subject line rules use 954,794 threads (6,628 human replies, 61 sending workspaces).
- A human reply is the recipient replied at least once with a reply that is not an auto-reply, out-of-office, bounce, warm-up, test or spam (sending tool's labels). An interested reply means at least one of those replies was labeled 'possibly interested'.
- A script turned each email body into traits (paragraphs, questions, the ask in the last paragraph, stats, greeting, P.S.) and dropped the text. No email, subject line, address or client is published.
- A rule is listed when following it got at least 10% more human replies per email than breaking it, overall and with the largest sender removed, with 10,000+ emails on each side.
- Left out: any group with fewer than 2,000 emails, or where one sending workspace made more than 45% of them. The newest 14 days are left out so replies can arrive.
- The page is regenerated from the data each time it is recomputed, so a rule that stops holding drops off.
What gets cold emails the most replies?
In 1,161,237 first emails Sales.co sent, the widest gap in interested replies among the 11 rules came from the ask. The 555,762 emails that offered to send something (a video, a list, an example) got 0.77% human replies per email, against 0.53% for the 157,733 that asked for a call or meeting, and 2.4x the interested replies.
Should you ask for a meeting in a cold email?
Not in the first email. Asking for a call got 0.53% human replies and 0.10% interested replies per email. Offering to send something got 0.77% and 0.25%. The gap held with the largest sender removed (0.69% vs 0.50%).
How long should a cold email subject line be?
5 to 7 words did best: 0.83% human replies per email, against 0.48% for 1 to 2 word subjects, out of 954,794 first emails. Subjects with the recipient's first name got 0.90% against 0.58% without it.
How long should a cold email be?
Word count made no clear difference once the largest sender was removed. Paragraph count did: emails with 1 to 2 paragraphs got 0.84% human replies per email, against 0.58% for 7 or more.
Do statistics help a cold email?
No. Emails with a percentage or "Nx" figure in the body got 0.64% human replies and 0.16% interested replies per email, against 0.72% and 0.21% without one.
Should a cold email have a P.S.?
Yes. Emails with a P.S. got 0.89% human replies per email against 0.69% without one, and 0.77% vs 0.62% with the largest sender removed.
Sources, as of November 9, 2026
- Sales.co sending database, email text: 1,161,237 first cold emails and 8,168 human replies from 58 sending workspaces, October 6, 2025 to October 25, 2026, as of November 9, 2026.
- Sales.co sending database, subject lines: 954,794 first cold emails and 6,628 human replies from 61 sending workspaces, October 6, 2025 to October 25, 2026, as of November 9, 2026.
- Sales.co pricing and plans: sales.co/pricing, read October 25, 2026.
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