How to Write Email Subject Lines People Actually Open
The subject line decides whether an email is read. These principles, with examples, help you write subject lines that are clear, specific and honest, without resorting to clickbait.
Your subject line competes with dozens of other messages in a crowded inbox. People decide in a second whether to open, ignore or delete. The best subject lines are not clever; they make the value of opening obvious.
Be clear before you are creative
"Your March invoice is ready" will always be opened by the right person. "Something exciting inside!" tells nobody anything. State what the email contains or what the reader gets.
Be specific
Specific details signal useful content: "5 tax deadlines for small businesses this quarter" beats "Important tax information". Numbers, names and concrete outcomes help.
Keep the key words early
Many people read email on phones, where long subject lines are cut off. Put the most important words first and aim for something that makes sense even if only the first 30 to 40 characters are visible.
Use the preview text
The preview text (preheader) appears next to or below the subject line in most inboxes. Use it to add a second piece of information rather than repeating the subject. If you leave it blank, many inboxes show the first line of the email, which is often "View in browser".
Personalise thoughtfully
Adding a first name can help, but relevance matters more. Segmenting your list so people receive content that matches their interests beats inserting a name into a generic message.
Avoid what damages trust
- Fake "RE:" or "FWD:" prefixes that imply an existing conversation
- False urgency or deadlines that do not exist
- All capitals and strings of exclamation marks
- Subject lines that do not match the content
Misleading subject lines can lead to spam complaints, which harm deliverability for every future email. Major mailbox providers watch complaint rates closely; Google's sender guidelines explain the thresholds and the authentication bulk senders need. Our article on SPF, DKIM and DMARC covers the technical side.
Test, but test properly
Many email platforms let you send two subject lines to a sample of your list and send the winner to the rest. Test one variable at a time, use a large enough sample to be meaningful, and judge by clicks or conversions as well as opens, since some privacy features make open rates unreliable.
A quick formula to start
Specific benefit + audience or context, for example "A 15-minute month-end checklist for freelancers". Then write five alternatives and pick the clearest.
Cover photo by Jonas Leupe on Unsplash.
