Your subject line decides whether your email gets read. 9 rules, and the test almost nobody runs

Why the subject line matters so much

In the inbox your email gets one second and three lines: the sender name, the subject and the preview text. That’s all people see before they decide. You can write the best newsletter of your life: if the subject doesn’t persuade, nobody reads it.

Treat the subject like the headline of an ad. It has one job: to get the next line read.

9 rules for subject lines that get opened

1. Say what’s inside. “Our autumn menu is here” beats “News!!!”.
2. Put the important words first. On phones the end often gets cut off.
3. Use numbers. “3 gift ideas under €30” is concrete, and concrete things get opened.
4. Talk about them, not you. “Your order” and “for you” pull harder than “our new collection”.
5. Ask a real question the reader wants to answer: “Booked for Saturday yet?”
6. Use their name sparingly. A name in the subject stands out, but use it every time and it stops working.
7. No CAPITALS and no “!!!”. They look like shouting and push away your best customers.
8. Deadlines only when they’re real. “Last day” works once; made up, it burns your credibility.
9. Keep the promise. A misleading subject gets one open and a lifetime unsubscribe.

Don’t forget the preview text

The preview text (or preheader) is the grey line that shows after the subject. If you don’t write it, the email app shows the first words of your email: often “View in browser” or an address. Wasted space.

Use it to finish the subject. Subject: “Our autumn menu is here”. Preview: “pumpkin, mushrooms and a dessert you won’t expect, from Thursday”. In Spedito the Preview field sits right under the subject of every email.

Do “spam words” really exist?

Less than people think. Today’s filters look mainly at who you are (an authenticated domain), how your list behaves (opens, complaints) and the message as a whole, not a single word like “free”.

But a shouty subject full of symbols and over-the-top promises makes people hit “report spam”, and that’s what sends you to the spam folder. For the technical side, read why emails go to spam.

The test that makes the difference: A/B testing subject lines

People who’ve written subject lines for twenty years don’t guess much better than you: they test. The method is simple:

1. write two different subject lines for the same email;
2. send each one to a small part of your list;
3. after a few hours, see which got more opens;
4. send the winner to everyone else.

In Spedito the subject line A/B test does it all for you (writing an email). Short of ideas? Our free subject line generator suggests five and tells you what to improve in the one you wrote.

Subject line examples for every occasion

• Something new: “The seeded loaf you kept asking for is here”
• Offer: “Subscribers only: 20% off until Sunday”
• Event: “Thursday tasting: 8 seats left”
• Useful tip: “How to keep bread fresh for three days”
• Win-back: “Should we keep writing to you?”

None of these is magic. They work because they’re clear, they speak to the customer and they deliver what they promise.

Frequently asked questions