You can write a great email, but if nobody opens it, it doesn’t matter. The subject line decides whether your message gets read or deleted. And when you’re writing an email between jobs, it’s usually the part that gets the least time.
Inboxes are crowded, and most emails get a split-second glance before someone opens, skips, or deletes. That decision rests almost entirely on the subject line, so it’s worth a few extra minutes.
What Your Subject Line Actually Has to Do
A subject line has one job: get the email opened. Not sell something. Not summarize the whole email. Not be clever for its own sake. Just earn a click from someone skimming their inbox.
That means your subject line needs to pass a simple test: does it give the reader a clear reason to open this email right now? The best subject lines do this by being specific, honest, and relevant to the person reading them. The worst ones are vague, generic, or so clearly promotional that they feel like spam before the reader even opens them.
What Actually Gets Opened
Decades of email marketing testing have revealed some consistent patterns. Here’s what tends to work:
Specific beats vague. “October news from the studio” is vague. “New fall classes start October 7, two spots left” is specific. Specific subject lines make a clear promise: open this, and you’ll find out exactly this.
Numbers and lists signal easy reading. “5 things to know before hiring a contractor” or “3 new menu items worth trying this month” perform well because they tell the reader immediately how much they’re committing to. People are more willing to open something when they know approximately what they’re getting into.
First names still work. Using the recipient’s first name, like “Sarah, your fall appointment window is open,” still tends to lift opens. Most email platforms make this easy with merge tags.
Curiosity works when it’s honest. A subject line that creates a genuine question in the reader’s mind can be effective: “We tried something new this month” or “This is the question we get most often.” The email just has to pay it off right away. If you tease and then don’t pay off, readers feel tricked and your open rates will drop over time.
Short and mobile-friendly wins. Most emails are opened on mobile devices first. Subject lines over 50 characters often get cut off. Aim for roughly 35 to 50 characters: enough to say something specific without getting cut off.
What Gets Deleted
Just as predictably, certain subject line patterns consistently underperform:
“Check out our latest newsletter.” This tells the reader nothing about why they’d want to open it.
ALL CAPS or lots of punctuation!!! Spam filters flag these, and readers associate them with low-quality mass email.
Misleading subject lines. “Re: your inquiry” when there was no inquiry, or “Quick question” on a promotional email. They might get one open, but they cost you trust and unsubscribes.
“Don’t miss out on this amazing opportunity.” Generic urgency gets tuned out. If something really is time-sensitive, say what it is and when it ends.
A blank or wasted preview line. The preview text that shows after the subject line in most inboxes is a second chance to earn the open. If it’s blank, repeats the subject line, or defaults to “View in browser,” that space is going to waste.
Testing Your Subject Lines
Most email platforms, including Mailchimp, Klaviyo, Flodesk, and Kit, offer A/B testing. You send two versions with different subject lines to part of your list, and the platform sends the better performer to everyone else. It takes about 30 extra seconds and, over time, shows you what your audience responds to.
Even without formal testing, it’s worth glancing at your open rates and noting which subject lines did best. Your audience is your own. General advice is a good starting point, but your own results will eventually tell you more than any industry average.
Write the Subject Line Last
One tip that makes a real difference: write the email first. Then ask what the single most interesting or useful thing in it is. That, said specifically and briefly, is usually your best subject line. Write it first and you’re guessing. Write it last and you know exactly what’s inside.
Subject lines are short, often under ten words, but they decide whether the rest of your effort gets read. A few extra minutes on them is time well spent.
If you’d like help with your email campaigns, from subject lines to the whole send, here’s how I handle email marketing. Or get in touch and I’ll take a look at what you’re sending now.