The email subject line: write it for the click, not the open
The one line everybody in the inbox reads. Its job is to get the right people to open, and they decide in the handful of words a phone shows.
- 127Subject Line
- The title of your email, crucial for grabbing attention and encouraging opens.
- Read alongside
- The sender name and the preview text, as one unit
- Judge it by
- Clicks and placed orders per recipient, not opens
- Never
- Promise what the email doesn't contain, or fake a reply with Re:
Three lines decide the open, and the subject is only the middle one
Look at your inbox on your phone. Every email arrives as three lines: who it's from, the subject, and a strip of preview text underneath. People read them together, in roughly the time it takes to scroll past.
- The sender name: your shop's name, spelled the way customers say it
- The subject: the point of the email, in the first few words
- The preview text: the detail that earns the tap
A phone cuts the subject short, and where depends on the phone. So the product, the offer or the deadline goes first. Anything after it is a bonus.
What a shop's subject line should actually say
Clear beats clever in a shop's inbox. Your customers aren't solving puzzles on the bus. They're deciding, in a second, whether this email's about something they want. So name the thing.
| The email | Says nothing | Says something |
|---|---|---|
| A restock | It's back | The linen shirt is back in navy |
| A launch | Something new is here | Meet the travel mug that fits your car's cup holder |
| An offer ending | Last chance | Free delivery ends tonight |
| A cart reminder | Did you forget something? | Your trainers are still in your basket |
None of the better lines needs an emoji or capitals. Both can help a line stand out, and both can look cheap on a premium brand. If the words say nothing, shouting them won't help.
Testing subject lines when Apple opens the email for you
Here's the awkward bit. Apple Mail can open your email in the background whether anyone reads it or not, so a test judged on opens is partly a count of iPhones. That's the whole story behind an inflated open rate.
- Test one idea at a time, like the product first against the offer first
- Pick the winner on clicks, or on placed orders if the list is big enough
- Send each version to enough people that the gap means something
- Write down what won and why, so the next test starts from there
One test proves next to nothing. A run of them, written down, tells you what your customers respond to. That's the asset.
The subject lines that win the open and lose the customer
Fake replies are the classic. Google's sender guidelines tell senders not to start a subject with Re: or Fwd: unless the email is a real reply or forward.
Sending to the US? The FTC's CAN-SPAM guide says the subject line must accurately reflect what's in the message. So no discount that isn't in the email, and no fake delivery alarm that turns out to be a sale. Each one buys a click and spends trust you'll want back later. That's the published rule, not legal advice.
Related terms
FAQs
How long should an email subject line be?
Long enough to say the thing, short enough that the important words land before a phone cuts it off. There's no single safe length, because every phone and inbox cuts in a different place. Put the product, offer or deadline in the first few words and treat the rest as extra for bigger screens.
Should I put the customer's first name in the subject line?
You can, as long as there's a fallback for people with no name saved, or the line goes out with a gap in it. Just don't expect much from it. A name won't rescue a subject that says nothing, and the product someone looked at tells you far more than the name they typed.
Which words send a subject line to spam?
Very few, on their own. Gmail and the other big inboxes judge the sender first: authentication, complaints and whether people engage with your mail. A sender in good standing can use the word sale in a subject line. A sender with a poor reputation lands in spam whatever the subject says.
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