Why Em Dashes Make Your Email Look AI-Written, and What to Use Instead

The dash that gave AI away

Sometime in 2024 people noticed that ChatGPT emails were full of long dashes. By 2025 it was a running joke: an email with three em dashes in it was assumed to be machine-written, no matter who actually wrote it.

The joke has a real basis. Language models learned to write from a huge amount of edited, published text (books, magazines, news sites), where the em dash is common. So they use it a lot.

Most people writing email do not, for a simple reason: there is no em dash key. On a Mac you press Option, Shift and the hyphen. On Windows it is Alt plus 0151 on the number pad. Almost nobody bothers for a quick reply.

So when a reader sees a long dash in a two-line email, they draw a conclusion. Fair or not, it changes how they read everything after it.

Which dash is which

Three dashes look alike:

• The hyphen (-) joins words, as in "follow-up" or "two-day".
• The en dash (–) shows a range, as in "9–5" or "pages 10–14".
• The em dash (—) is the long one. It sets off an aside or a sudden turn.

Only the em dash is the problem. Hyphens are fine. En dashes are rare enough that nobody notices them, though in an email "9 to 5" reads more naturally anyway.

Four ways to replace an em dash

Nearly every em dash can become one of four things. Pick based on what the dash was doing in the sentence.

A period, when it joins two thoughts

Before: "We moved the launch to May — the payment provider needs more time."

After: "We moved the launch to May. The payment provider needs more time."

Commas, when it adds a small detail

Before: "Our new hire — Dana from the Berlin office — starts Monday."

After: "Our new hire, Dana from the Berlin office, starts Monday."

Brackets, when it really is an aside

Before: "The invoice — the one from March — is still unpaid."

After: "The invoice (the one from March) is still unpaid."

A colon, when it introduces something

Before: "There's one thing left — the signed contract."

After: "There's one thing left: the signed contract."

If none of these fit, the sentence is probably doing two jobs. Split it into two.

Is it ever fine to keep one?

Yes. If you have always used em dashes, keep using them in your own writing. Writers used them for centuries before chatbots did, and one dash in an email that otherwise sounds like you will not make anyone suspicious.

The giveaway is the pattern: three or four in one email, each setting up a neat little reveal, like "The result — a 40% increase." That rhythm is what readers recognize. When you cut the dashes, you usually cut the rhythm too.

Dashes are only half of it

Em dashes get attention because they are easy to spot. A draft with every dash removed can still sound generated. Watch for these as well:

• An opening line that thanks the reader for reaching out
• Everything grouped in threes
• Words like "delve", "seamless" and "robust"
• "It's not just X, it's Y"
• A closing line offering to answer any questions

Our guide on how to make an email sound human goes through each of these with a before and after.

Catch them before you send

If you draft with AI, the dashes will keep coming back no matter how often you delete them. Presend checks every email and message when you click send and flags writing that reads like a chatbot wrote it. You can also add a rule of your own in plain English, such as "Warn me if a message has more than one em dash", and choose whether it warns you or stops the send.