What is an email subject line actually for?
Every clickbait subject line borrows an open from your next email, and your subscribers always collect on the debt. A subject line has one job, which is to earn the open. Not to summarize, not to sell. That makes the game honest curiosity: give the reader a reason to look inside, then make sure the email pays it off. Everything below is a pattern that respects that rule.
These are newsletter and marketing subject lines, written for people who opted in to hear from you. If you’re emailing strangers, read cold email subject lines that get opened instead; the rules change when nobody asked for your email.
Which email subject line patterns get opens?
Four patterns cover almost every line worth sending. The examples below illustrate each pattern; they aren’t results from a real send.
The specific number
"3 fixes for a quiet reply rate" beats "how to get more replies."
The honest gap
Say enough to intrigue and stop before you satisfy. The email closes the loop, which is the part clickbait skips.
The pattern break
A plain, lowercase, personal line in a promotional inbox stands out precisely because it doesn’t look like marketing.
The direct benefit
When the value is obvious, say it plainly. Cleverness here only gets in the way.
The two things people forget
You can write a perfect subject line and still lose the open to the two fields sitting on either side of it.
Sender name
People decide based on who it’s from before they read the subject at all. A name they trust will outpull a clever line from a stranger.
Preview text
Treat it as the second half of the subject line, not a throwaway. Leave it blank and the inbox fills it with whatever text comes first, which is rarely your best sentence. (Marketers also call this the preheader.) Write the subject and preview text together, as one message.
Which subject line habits should you stop?
Fake "Re:" and "Fwd:" prefixes, false urgency, and anything that reads as a trick. A trick works once, then trains people to distrust you, and that distrust shows up as lower opens and more spam complaints on every send after it. If your opens have been sliding, look at reputation before you blame your wording. See the deliverability guide.
Test before you trust
Your list decides, not me. A line that won for someone else can lose on yours, so split-test your next few sends. My A/B testing guide covers how to do it without fooling yourself with tiny samples, and the free subject line tester is a quick sanity check before you hit send.
Subject-line split testing is built into most major platforms, including Kit, ActiveCampaign and MailerLite; check the plan you’re on before you count on it. If you’re still choosing a platform, start with our best email marketing software picks.
Every subject line is a small promise. Clever writers win an open. Writers who keep their promises win the inbox, because eventually people stop reading your subject lines and start opening your name.
— Carlos Gil, Founder & Editor, The Best NetworkFrequently asked questions
It varies by list, industry and audience, and Apple Mail Privacy Protection inflates opens for everyone. The useful comparison is your own last ten sends: if a subject line beats your recent average, it worked. See the benchmarks post for sourced industry figures.
Short enough to read on a phone without the meaning getting cut off. Front-load the words that matter, because mobile inboxes truncate long lines, and let the preview text carry the rest of the message.
Sometimes, for the right audience. An emoji can make a line stand out in a crowded inbox, but it can also read as promotional. Split-test it on your own list and never rely on an emoji to carry the message.
Newsletter and marketing subject lines go to people who opted in, so a recognizable sender name and an honest curiosity gap do most of the work. Cold email goes to strangers who never asked to hear from you, which changes the rules. For that, read cold email subject lines that get opened.
No. A misleading subject line can win one open, but the reader notices when the email doesn’t deliver. That disappointment shows up later as ignored sends, unsubscribes and spam complaints, which damage the sender reputation every future email depends on.
I keep picking apart what earns the open in Inbox Gold, my LinkedIn newsletter on email marketing.