How to Write Email Subject Lines That Actually Get Opened
How many emails did you ignore today? Ten? Twenty? You glanced at the subject line, decided it wasn’t worth your time, and left it to rot in your inbox graveyard.
When brands are battling it out in the inbox, it’s that split-second decision-maker between “open” and “delete.” Between revenue earned and revenue lost.
In this post, we’ll show you how to write subject lines that actually earn the open, why most brands get it wrong, and the exact strategies we use at ECD to keep our clients out of the spammy pile and in the “must-read” zone.
Why Subject Lines Matter So Much
You’ve got 30 to 40 characters tops before your subject line gets cut off in a mobile inbox. That tiny slice of real estate decides whether your email gets opened, ignored, or trashed.
But it’s more than just curiosity. The subject line sets expectations. Get it right, and you build trust. Get it wrong, and you waste the send—and worse, you train people to scroll past you next time.
For e-commerce brands, open rates aren’t vanity metrics. They’re proof that your emails are earning attention instead of getting buried.
Best Practices for Writing Great Subject Lines
There’s no magic formula. If there were, every inbox would look the same…and you’d ignore those emails, too.
What works most often:
- Short. Aim for under 40 characters on mobile.
- Human. Write like a person. No corporate filler.
- Specific. Numbers, deadlines, product names. Not vague hype.
- On-brand. Keep the tone people recognize from you.
- Trustworthy. Pay off the promise inside the email.
Preview text matters. It’s the second half of your pitch. Use it to finish the thought, not repeat the subject line.
Types of Subject Lines That Work
Every send has a job to do. The subject line should match it.
Promotional Subject Lines
Promotions are easy to blast but hard to get right. “25% off everything” is fine, but it won’t stand out when a hundred other brands send the same line. The subject lines that work lead with what the customer gains or loses if they wait. Scarcity, specificity, and timing make the offer feel urgent without sounding desperate.
- Last chance: 25% off ends tonight
- Only 2 left in stock
- An exclusive gift for our VIPs
- Did you forget your free plant?
Product Launches
The worst launch subject line is “New product alert.” Nobody clicks because something exists. They click because it fixes a problem or makes life better. Strong launch subject lines frame the release around the impact, not the announcement.
- Save Your Back and Your Weekend
- Solve Winter Skin in 2 Steps
- Set-it-and-forget-it Annuals Are Here!
- Two Reasons to Celebrate
Content Emails
These are overlooked, but they build long-term trust. The subject line needs to spark curiosity or promise insight, not bury the value under “Read our blog.” Done right, these lines make people click because they can’t help but want the answer.
- You’re Probably Watering Wrong…
- 12 Reasons Pros Plant In Fall
- The Deliverability Fix Most Brands Miss
- How’s Your Garden Coming Along?
Urgency or FOMO
Urgency is one of the strongest tools in subject lines, but only when the deadline is real. If you say “last chance” every week, people stop believing you. Used sparingly and backed by truth, these lines drive action fast.
- It’s in 5 Other Carts…
- Don’t Tell Me You Forgot This
- Sale ends at 11:59 pm EST.
- Your Cart Expires in 30 Minutes
Personalization
Go beyond first names. Better personalization uses behavior or context: what someone browsed, where they live, or what they’ve already bought. Done well, it feels like a one-to-one note.
- Your Boots Are Back!
- Zone 7B Can Still Plant!
- Don’t Let Her Go Again
- I Guess It Was Meant to Be
Keep it natural. Robotic personalization reads creepy.
What to Avoid When Writing Subject Lines
Most mistakes boil down to breaking trust:
Tone mismatch.
When the subject line promises something sharp or exciting but the email inside doesn’t deliver, readers stop clicking.
Tricks and gimmicks.
ALL CAPS, emoji spam, or fake “Re:” lines might grab attention once, but they scream desperation and trigger spam filters.
Guessing instead of testing.
Skipping A/B tests means you’re assuming what works. Even small tweaks can swing results—you only know by testing.
Voice drift.
A brand that suddenly changes tone feels inconsistent. Premium brands can’t sound like TikTok trends overnight, and playful brands shouldn’t go stiff for a sale.
How ECD Helps Brands Lift Open Rates
At ECD, we don’t stop at clever lines. We measure what they deliver. After an audit, our clients typically see 15–30% lifts in open rates, stronger inbox placement, and flow performance that drives up to 40% of total email revenue.
In many cases, revenue per recipient climbs 20–50% within the first 90 days.
The subject line may be a few words, but it’s often the switch that powers the whole system.
Ready to flip it on for your brand?
Written by: Facundo Zocola
Senior Email Marketing Manager by day, and travel enthusiast always, Facundo brings an explorer’s curiosity and a tactician’s brain to every part of the customer journey. Equal parts strategist and all-around nice guy, he believes great email marketing isn’t just clever—it’s clear, intentional, and always respectful of your time. Whether he's in your inbox, scoring a goal, or enjoying a pint of ice cream, the aim is always the same: making every win meaningful.