Can prospects tell your cold email was written by AI?
Some can and some can't, and in the research the best spotters are people who often use AI for their own writing. Two studies frame it.
- Most people guess badly. In a study by Maurice Jakesch, Jeffrey Hancock and Mor Naaman, published in PNAS in 2023 and first posted in June 2022, 4,600 participants across six experiments could not detect self-presentations written by the AI models of the time, in professional, hospitality and dating contexts. Their judgements leaned on flawed rules of thumb, such as treating first-person pronouns, contractions or mentions of family as signs of a human writer.
- Heavy AI users guess well. In a 2025 study by Jenna Russell, Marzena Karpinska and Mohit Iyyer, annotators who often use AI for their own writing read 300 non-fiction articles, some written by GPT-4o, Claude or o1. A majority vote of five such annotators misclassified only 1 of the 300, and beat most of the detection tools tested, even when the AI text had been paraphrased or humanised.
Neither study tested cold email, so treat this as a guide. Our reading: a founder or sales leader who drafts with ChatGPT every day resembles the expert readers in the 2025 study, though those experts judged full articles and were pooled by majority vote. If you sell to people like that, expect some of them to notice.
Does it hurt if they think AI wrote it?
It can, once the reader believes it. The studies measure trust, and none of them measures replies, yet they point the same way.
- The replicant effect (2019). In three experiments reported by Cornell and Stanford researchers, people rated real Airbnb host profiles. When told all the profiles were human-written or all AI-written, they trusted them about equally. When told the set was mixed, they distrusted the profiles they believed were AI-written, even though real hosts had written all of them.
- Disclosed AI use (2025). In a survey of 1,100 professionals by Anthony Coman and Peter Cardon, reported by the University of Florida, people rated a supervisor's congratulatory email after being told how much AI helped write it. 83% saw the supervisor as sincere when the message had low assistance, against 40% to 52% for high assistance. 95% found the low-assistance version professional, against 69% to 73% for high assistance.
A cold inbox is a mixed set, which is the condition where the 2019 study found distrust. That link is our inference; the 2019 study used Airbnb profiles, and the 2025 one used workplace messages.
Reply-rate evidence is thinner. In one r/coldemail post from March 2026, a company that built an AI writing agent reported 300 sends each: 5.9% replies for the agent and 4.8% for a professional writer. By our arithmetic that gap is about three replies (17.7 against 14.4), and neither rate works out to a whole number of replies from exactly 300 sends, so the figures are rounded or the base differs. It is a vendor's own small test. For LinkedIn, our breakdown of Expandi's data on AI-written messages covers a larger comparison.
Which tells do readers actually name?
Readers name the same small set of tells, and most are about padding and polish. This table pulls together what commenters on Hacker News and Reddit named, alongside Wikipedia's field guide to signs of AI writing, an advice page from its volunteer AI Cleanup project:
| Tell | Who named it | What to write instead |
|---|---|---|
| Em dashes, or a mix of dashes and hyphens | Hacker News commenters, 2025; Wikipedia guide | Commas and full stops. Removing dashes alone won't fix the rest. |
| Bold text in an email | Hacker News commenter; Wikipedia guide | No formatting at all |
| Superlatives, adjectives and clichés | Hacker News commenter; Wikipedia guide (promotional language) | One plain claim with a number |
| Polish that doesn't match the sender | Hacker News commenter | Write the way you write to colleagues |
| Groups of three and contrast phrases | Wikipedia guide (rule of three, negative parallelisms) | One reason, one ask |
| Facts about the prospect that aren't true | r/coldemail poster, 2026 | Only facts you opened yourself |
The em dash tell is fading. The Wikipedia guide says some AI companies have tried to make newer chatbots suppress em dashes, naming OpenAI's GPT-5.1. It also warns that not all text with these signs is AI-generated, and that humans are bad at telling the two apart.
The deeper tell is vagueness. The guide explains that AI models tend to drop specific, unusual facts and replace them with generic, positive descriptions. In email, that looks like praise that fits any company. One Hacker News commenter in March 2025 described an AI-written email with dashes, bold text, superlatives and unusually perfect English. A reply summed up the feel: "If you can clearly read it in your head in that new sassy GPT voice, it's probably LLM".
What practitioner threads keep repeating
Across the three r/coldemail threads and three Hacker News discussions we read, the same four patterns keep coming back.
The accusation lands on the post itself
In an April 2026 thread arguing that AI emails make human-written ones stand out, two commenters said the post read as AI-written, one pointing at the phrase "the opportunity nobody's talking about". On a May 2025 Hacker News thread about AI-written messages, one commenter suspected the linked article was AI-assisted, and another pointed to em dashes mixed with hyphens. Readers are primed to look.
False positives are common
In the same Hacker News thread, another commenter objected that people who learned to type em dashes properly now get mistaken for AI. In a March 2026 thread on whether AI cold emails sound like garbage, one commenter asked whether anything formatted properly now smells like AI.
Fake typos are already a tell
In the April thread, the poster listed intentional typos as something that now works. One reply said people are doing the fake-typo thing too, so that window is closing.
Research decides it
The March thread's poster said AI tools either produced generic openers or made up facts about the prospect. Several replies said to use AI to gather checkable facts, and one added that it should say when it found nothing. On a March 2026 Hacker News question about AI for cold email copy, one reply asked senders to read the recipient's website first and say where they saw the need.
How do you make a cold email read as yours?
Give it one fact only a person who looked could know, and cut everything that would fit any company. Here is the same email both ways. The company and roles are invented for the example.
The before version has several of the tells above: vague praise, a group of three, a stock ask. The after version has one checkable fact, one question and one small offer. Use this check on every draft:
- Could this opening line be sent to a different company unchanged? Rewrite it.
- Did you open the page behind every fact? If not, cut the fact.
- Read it aloud. If it doesn't sound like you on a call, change the words that don't.
- Delete adjectives that praise them, and any sentence that only sets up the next one.
- Keep one ask, small enough to answer from a phone.
For where to find the fact, our guide to Becc Holland's premise research gives a three-minute method. Our cold email opening lines show the shape of a specific first sentence.
How much AI help is fine?
Light help is fine; the risk grows with how much of the message the AI wrote. In the 2025 University of Florida survey, low assistance such as grammar or editing was generally acceptable, while higher levels triggered negative views of the sender. The researchers suggested AI suits routine, informational messages, and that relationship messages are better handled with minimal AI. A cold email asks a stranger to start a relationship, so we put it in the second group.
A split that follows that research: let AI find and check facts, tidy grammar and shorten your draft. Write the opening fact and the ask yourself. If a tool writes the full message, make sure it starts from something real about the person.
On LinkedIn and X, Siela's AI SDR starts from something real about the person: each message is written for that person from their profile and the signal that surfaced them, then checked by a second AI reviewer before it is sent. For email, the first message is your own template with each person's name, company and title filled in. Whether you must say a message involved AI is a separate legal question; our guide to EU AI Act Article 50 for sales teams covers when the law requires it.
Frequently asked questions
Do AI detectors catch AI-written cold emails?
Not reliably. Wikipedia's guide to signs of AI writing tells its editors not to rely on detection tools alone, because they have non-trivial error rates and can be thrown off by paraphrasing. A 2025 study found that five annotators who often use AI for writing beat most detectors it tested on 300 articles, even after the AI text was paraphrased or humanised.
Will removing em dashes make an AI email look human?
No. Em dashes are one tell among many, and Wikipedia's guide notes that some AI companies have tried to make newer chatbots suppress them. Readers and Wikipedia's guide also flag bold text, superlatives, groups of three, praise that fits any company and facts that turn out to be wrong. Changing punctuation leaves all of those in place.
Is it bad to use ChatGPT to write a cold email?
Using it for research, grammar and shortening is low-risk; letting it write the whole message is where trust drops. A 2025 University of Florida survey of 1,100 professionals found low assistance such as editing was generally acceptable, while 83% saw the supervisor as sincere with low assistance, against 40% to 52% with high assistance.
Why do accurate, well-formatted emails get called AI?
Because readers are now primed to look for AI, and polish has become one of the cues. In 2025 and 2026 threads on Hacker News and r/coldemail, commenters complained that careful punctuation and tidy formatting get mistaken for AI. A 2023 PNAS study also found people rely on flawed rules of thumb when judging whether text is human.
Sources
- Jakesch, Hancock and Naaman: Human heuristics for AI-generated language are flawed (PNAS; arXiv 2206.07271) (first posted 15 Jun 2022, revised 14 Mar 2023)
- Russell, Karpinska and Iyyer: People who frequently use ChatGPT for writing tasks are accurate and robust detectors of AI-generated text (arXiv 2501.15654) (26 Jan 2025, revised 19 May 2025)
- Cornell Chronicle: AI-generated profiles? Airbnb users prefer a human touch (24 Apr 2019)
- University of Florida News: Is writing with AI at work undermining your credibility? (6 Aug 2025)
- Wikipedia: Signs of AI writing (WikiProject AI Cleanup advice page) (checked 24 Oct 2026)
- Hacker News comment thread on an AI-written email (5 Mar 2025)
- Hacker News: You sent the message, but did you write it? (3 May 2025)
- Hacker News: Do you use AI for cold email copy? (20 Mar 2026)
- r/coldemail: Anyone else feel like AI-written cold emails still sound like garbage? (19 Mar 2026)
- r/coldemail: AI-generated cold emails are making human-written ones print money (12 Apr 2026)
- r/coldemail: We ran 300 cold emails written by a professional vs an AI agent (23 Mar 2026)